Add request correlation and per-request database telemetry

[samgbafa]

Part of TC-959.

Changes

• Validate, normalize and echo request UUIDs; emit typed request-completion events with scoped database timings.
• Use keyed account/space pseudonyms without adding raw identifiers, SQL or parameters to request events.
• Share one startup-derived core pseudonymizer with length-prefixed database hashing and literal synthetic fixtures for F6 reuse.
• Require explicit first-party origins for correlation forwarding. Document key custody, restart stability and instrumentation coverage/exclusions.

Verification

Head: a9bed3209be9082a639d7d6fafcf6e2846070391, after a normal current-main merge.

• Rust/native CI: workspace 1,201 passed, 12 ignored; DuckDB core 550 passed, including literal vectors; native suites 15 passed, including leak-canary and timing/identity controls.
• Container validation and release planning passed; deployment/publication jobs skipped.
• Exact-head Opus resolution verdict; earlier source-review record.

No release, deployment, shipper/schema change or F6 instrumentation is included. Performance measurements are separate release-cut evidence.

[samgbafa]

Review record for TC-959:

• Astra, exact head e82447ed7dfb46e524cfbd32eddc4271fd2249e6: no actionable findings on the reviewed N2 production call paths.
• Opus, exact head df6a75c2b52b3ed482a0d2d9ed412bead63fdabc: helper-delta source clearance; reported findings resolved, nothing new.

These were source reviews. Current-main resolution review is recorded separately at its exact head; release/deployment decisions remain separate.

[samgbafa]

APPROVE: see TC-959 (reviewed exact head a9bed32)

https://linear.app/tinycloud-labs/issue/TC-959