docs(permissions): re-anchor the system-context census on the merged tree

`pnpm gen:system-context-census` on the merge commit. The first run refused
engine.ts (16 distinct page anchors vs 15 anchorable lines) because row 20
carried the branch tree's coordinate for the INSERT `isSystem` site while the
validation-row range carried main's coordinate for the same line; putting
row 20 on main's coordinate (the driver's "take either side") made the page
one coordinate system, after which the rerun rewrote 11 engine.ts anchors and
refused zero files. `pnpm check:system-context-census` is green: 106 sites in
19 packages across 44 files, 140 anchors resolve, 27 declared non-read.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ARYe3yQTQCUFm5qPYNgKaJ

Author: claude

content/docs/permissions/system-context.mdx

@@ -100,7 +100,7 @@ that silently does not happen.
 | 11 | Session-resolution middleware skipped | plugin-auth | Get: no session lookup attempted | `auth-plugin.ts:1412` |
 | 12 | Per-request performance timings disclosed | observability | Get: timing headers a normal caller cannot pull | `perf-timing.ts:474` |
 | 13 | Permission-set **overlay discard** skips the tenant-admin assertion | plugin-security | Get: an overlay can be discarded with no authenticated tenant administrator | `permission-set-overlay-discard.ts:142` |
-| 14 | MCP stdio bridge skips the object API-exposure gate | mcp | Get: the bridge reaches objects whose `apiEnabled` / `apiMethods` would refuse an external caller | `stdio-data-bridge.ts:246` |
+| 14 | MCP stdio bridge skips the object API-exposure gate | mcp | Get: the bridge reaches objects whose `apiEnabled` / `apiMethods` would refuse an external caller | `stdio-data-bridge.ts:250` |
 | 15 | **Read-audit rows are not written** | plugin-audit | Lose: the "a person opened this record" trail. `sudo()` keeps the caller's `userId`, so this flag is the only thing separating a human read from a platform one | `read-audit.ts:556` |
 | 16 | Approval snapshot payload redaction skipped | plugin-approvals | Get: the whole snapshot on `find` / `findOne` — the audit/replay channel. Lose: field-visibility redaction over approval payloads | `payload-redaction-middleware.ts:115` |
 | 17 | REST anonymous-deny seam satisfied | rest | Get: `enforceAuth` passes with no `userId`. Not reachable from the wire — `isSystem` is never set on an inbound request | `rest-server.ts:1585` |
@@ -109,17 +109,17 @@ that silently does not happen.
 
 | # | Behaviour when `isSystem` | Package | What you get / what you lose | Anchor |
 |:--|:---|:---|:---|:---|
-| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:11623` |
-| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11806` |
-| 20 | **`readonly` strip bypassed — INSERT** | objectql | Same, on create — one gate over BOTH create-side passes since the 2026-09-03 ruling moved the static-`readonly` strip in beside the runtime-owned one and deleted the DataProtocol ingress copy. `isSystem` is the **only** exemption on this path: `preserveAudit` is deliberately not read on create, so a non-system historical import is still stripped | `objectql/src/engine.ts:10193` |
-| 21 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:10404`, `readonly-strict-errors.ts:66` |
-| 22 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:6223` |
+| 18 | **`readonly` strip bypassed — UPDATE, single row** | objectql | Get: a `readonly` field CAN be written. Lose: the protection that stops a caller seeding e.g. `approval_status` | `objectql/src/engine.ts:11718` |
+| 19 | **`readonly` strip bypassed — UPDATE, bulk/predicate** | objectql | Same, on the multi-row path | `objectql/src/engine.ts:11901` |
+| 20 | **`readonly` strip bypassed — INSERT** | objectql | Same, on create — one gate over BOTH create-side passes since the 2026-09-03 ruling moved the static-`readonly` strip in beside the runtime-owned one and deleted the DataProtocol ingress copy. `isSystem` is the **only** exemption on this path: `preserveAudit` is deliberately not read on create, so a non-system historical import is still stripped | `objectql/src/engine.ts:10366` |
+| 21 | Strict-drop refusal never fires | objectql | Lose: a caller that opted into loud refusal gets **silence** — strict refuses exactly what the strip would have taken, and the strip took nothing | `objectql/src/engine.ts:10499`, `readonly-strict-errors.ts:66` |
+| 22 | **Referential-integrity check skipped** | objectql | Get: writes proceed against unreachable/unresolvable targets. Lose: an `isSystem` caller can write a **dangling reference** | `objectql/src/engine.ts:6225` |
 | 23 | Tenant-audit warning silenced; `bypassTenantAudit` threaded to the driver | objectql | Get: unscoped system writes stop warning. Lose: the signal that would flag a genuine user-path scoping bug | `objectql/src/engine.ts:3936`, `:3946`, `:3973` |
 | 24 | Engine-owned / append-only write guard bypassed | plugin-security | Get: generic writes to `managedBy` engine-owned objects | `system-write-guard.ts:96`, `:120` |
 | 25 | Identity write guard bypassed (ADR-0092) | plugin-auth | Get: direct writes to identity tables through the generic data path | `identity-write-guard.ts:99` |
-| 26 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6921` |
-| 27 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:12422` |
-| 28 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:12351` |
+| 26 | Search-companion column **kept** in a read's rows when it was explicitly requested | objectql | Get: the internal companion column is readable. Lose: nothing for app code — this is the engine reading its own index | `objectql/src/engine.ts:6924` |
+| 27 | Dependent-count disclosure on a blocked delete | objectql | Get: the count of blocking children. Nothing was elevated past the caller, so nothing is withheld | `objectql/src/engine.ts:12517` |
+| 28 | Reference-cleanup log attributes the write to `'system'` | objectql | Get: an honest actor label instead of `anonymous` when the context carries neither `userId` nor `actor` | `objectql/src/engine.ts:12446` |
 | 29 | **Bulk data event `organizationId` OMITTED** — the batch is published "not asserted" | objectql | Get: nothing — the `data.records.*` event still publishes. Lose: the per-organization attribution: the security middleware composed no tenant wall for a system write, so the producer cannot vouch that every row a predicate write affected belongs to one organization, and the key is omitted rather than filled from the caller's `tenantId`; a tenant-scoped consumer then does not deliver the event inside an organization wall (#15225) | `objectql/src/engine.ts:2371` |
 
 ### 3. Sharing (`plugin-sharing`)
@@ -180,7 +180,7 @@ a reader tracing where elevation travels needs them.
 | # | Site | Package | What it does |
 |:--|:---|:---|:---|
 | 62 | `objectql/src/engine.ts:3743` | objectql | Propagates `isSystem` into the hook session so hooks can tell engine self-writes from user writes |
-| 63 | `objectql/src/engine.ts:14866` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
+| 63 | `objectql/src/engine.ts:14961` | objectql | `ScopedContext.isSystem` getter — re-exposes the underlying execution context's flag |
 | 64 | `plugin-reports/src/report-service.ts:556` | plugin-reports | Threads the flag into the engine call that runs a report |
 | 65 | `body-runner.ts:279` | runtime | Rebuilds an `ExecutionContext` from a hook session, carrying the flag across |
 
@@ -195,8 +195,8 @@ assuming `isSystem` covers it is a documented source of bugs.
 |:---|:---|:---|
 | "It suppresses triggers / record-change automation" | **No.** Only `skipTriggers` does. A bare `{ isSystem: true }` on a seed write re-fired automation on freshly seeded rows and wedged first boot | `metadata-protocol/src/seed-loader.ts:2032` (rationale at `:1942`–`1944`, #3760), `flow.zod.ts:702` |
 | "It skips the state machine" | **No.** That is `skipStateMachine`, carried by seed replay and by `treatAsHistorical` imports | `objectql/src/engine.ts` FSM gate; see [State Machine](/docs/protocol/objectql/state-machine) |
-| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:10339`–`10356` |
-| "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1580` (#3493 / #6640) |
+| "It skips validation rules" | **No.** Field shape, `format`, `script` and the rest still run. The `readonly` strip runs *before* validation precisely so a discarded value is not judged | `objectql/src/engine.ts:10349`–`10366` |
+| "It preserves a supplied `updated_at` / `updated_by`" | **No.** That is `preserveAudit`, a separate opt-in — and an UPDATE-path exemption only | `field.zod.ts:1581` (#3493 / #6640) |
 | "It stamps `created_by`" | **No.** Audit stamping reads `userId` from the context. A user-less system write stamps nothing — that is today's behaviour, not an error | `runtime-identity.ts:280`–`281` |
 | "It bypasses every guard" | **No.** The last-admin guard applies to **every** context, `isSystem` included — the deprovision path that actually locks an org out is the system one | `last-admin-guard.ts:299` |
 | "A client can request it" | **No.** Never settable from inbound HTTP or from an action body | `rest-server.ts:1553`, `:1582`; `domains/actions.ts:414` |