chore: fix lint errors and modernize python syntax

.claude/CLAUDE.md

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+# CLAUDE.md
+
+<!-- Add your custom instructions below. Repowise will never modify anything outside the REPOWISE markers. -->
+<!-- Examples: coding style rules, test commands, workflow preferences, constraints -->
+
+<!-- REPOWISE:START — Do not edit below this line. Auto-generated by Repowise. -->
+## IMPORTANT: Codebase Intelligence Instructions for mcp-ariel-memory
+
+> This repository is indexed by [Repowise](https://repowise.dev).
+> Use the MCP tools below for orientation, discovery, and enriched context
+> (documentation, ownership, history, decisions). **Always verify against
+> actual source files before making changes** — the index may be stale.
+
+Last indexed: 2026-07-15 (commit 9a92a0f)
+### Entry Points
+- `__main__.py`
+- `mcp_server/server.py`
+### Tech Stack
+**Languages:** Python
+**Frameworks:** Pydantic
+
+**Infra:** Docker, Docker Compose### Architectural Layers
+| Layer | Files | Purpose |
+|-------|-------|---------|
+| Application | 66 |  |
+| Service | 5 |  |
+| Config | 19 |  |
+| Utility | 21 |  |
+| Docs & Tooling | 43 |  |
+| Test | 55 |  |
+
+### Guided Tour (12 steps)
+1. `README.md`
+2. `server.py`
+3. `__main__.py`
+4. `index.js`
+5. `connection.py`
+6. `config.py`
+... and 6 more steps
+### Hotspots (High Churn)
+| File | Churn | 90d Commits | Owner |
+|------|-------|-------------|-------|
+| `rag/engine.py` | 99.2th %ile | 32 | Ariel Memory |
+| `tests/test_mcp/test_tools_e2e.py` | 98.5th %ile | 9 | Ariel Memory |
+| `tests/test_hypothesis.py` | 97.7th %ile | 7 | Ariel Memory |
+| `mcp_server/tools_layer.py` | 96.9th %ile | 20 | Ariel Memory |
+| `shared/saga.py` | 96.2th %ile | 19 | Ariel Memory |
+
+## Code health
+Three signals: **defect risk** (the overall score), **maintainability** (smells that hurt readability/change-cost without predicting bugs), and **performance** (static performance RISK: I/O-in-loop / N+1 shapes that waste work, high-precision/low-recall). Maintainability and performance are co-equal views, never blended into the defect headline. See `docs/CODE_HEALTH.md`.
+
+Defect risk, Hotspot health: 4.74/10 (stable) ·
+Average: 7.11/10 ·
+Worst: 1.0/10 (`shared/saga.py`)
+Maintainability, Average: 8.71/10
+Performance risk, Average: 9.82/10
+
+### Critical biomarkers
+- `tests/test_integration.py` — churn risk — impact −2.4
+- `features/rate_limiting.py` — untested hotspot — impact −2.0
+- `features/audit_trail.py` — untested hotspot — impact −2.0
+- `graph/epistemic.py` — untested hotspot — impact −2.0
+- `graph/temporal.py` — untested hotspot — impact −2.0
+
+### Repowise MCP Tools
+
+This repo has the Repowise MCP server configured. The tools below answer questions `grep`/`Read` cannot. Every response carries an `_meta` envelope with `index_age_days`, `indexed_commit`, and a `stale_warning` only when the index has actually diverged from HEAD — silence means the index is current.
+
+**When to call which tool:**
+
+| Tool | What only this tool answers |
+|------|------------------------------|
+| `get_answer(question)` | Synthesised answer with citations and a content-grounded `confidence`. First call for "how does X work" / "where is Y" / "why is Z". Value questions may return `grounding: "extracted"` — the verbatim source line, no synthesis involved. On low confidence returns `best_guesses` with one-line justifications. |
+| `get_context(targets=[...])` | Triage card for files/modules/symbols — title, summary, signatures, `hotspot` bit, `decision_records` titles, `symbol_id`s. File targets auto-upgrade to a `verified` skeleton (every signature, ~37% of a full Read). `include=["callers"]` works on file targets too (import + call rollup). |
+| `get_symbol(...)` | Source bytes with live-verified bounds. Three forms: `"path.py::Name"` (indexed symbol), `"path.py:140-180"` (live range read, ≤200 lines), `"repowise#<hex>"` (omission ref). Index misses return `fallback_lines` from a live grep instead of a dead end. |
+| `search_codebase(query, mode?, kind?, symbol_kind?)` | Hybrid code search. `mode="auto"` (default) routes by query shape: an identifier → indexed symbol hits (`symbol_id`/`file`/line bounds — pipe into `get_symbol`), a path → file pages (pipe into `get_context`), prose → wiki-semantic search, mixed → hybrid (symbols first). Force a branch with `mode=symbol\|path\|concept\|hybrid`. Concept hits carry `search_method` (`embedding` vs `bm25` fallback); decision records rank below file pages unless the query is why-shaped. |
+| `get_why(query, targets?)` | Architectural decision archaeology — *why* the code is shaped this way. Call before refactors or pattern divergences. Falls back to git archaeology when no ADRs exist for a file. |
+| `get_risk(targets, changed_files?)` | What history says about touching these files: churn, owners, blast radius. Pass `changed_files` for PR mode → returns a `directive` (`will_break`, `missing_cochanges`, `missing_tests`). |
+| `get_health(targets?, include?)` | Code-health scores + biomarker findings (defect / maintainability / performance pillars). Self-check before a PR — read the same signals the merge-gate judges your change on. Default is lean; opt in with `include`: `["accuracy"]` (does the score rank the buggy files first — precision@K + `lift`), `["signals"]` (per-file prior-defects / churn / owners / degree, targeted mode), `["churn_complexity"]` (volatile-and-complex danger-zone files), `["biomarkers"]` (all findings), and a dimension name `["performance"]` / `["defect"]` / `["maintainability"]` to filter findings to one pillar. |
+| `get_dead_code(...)` | Tiered unreachable / unused-export / zombie-package findings. Run before a cleanup sprint, not before a targeted fix. |
+| `get_overview(repo?)` | Architecture map + `tool_guide` recipes. One-time orientation; skip on subsequent calls in the same session. |
+
+**Trust protocol — when a response replaces reading the source:**
+- `verified: true` on any response means the served content was checked against the live working tree. **Never follow a verified response with a Read of the same lines** — you would be paying twice for identical bytes.
+- `get_answer` with `confidence: "high"` or `grounding: "extracted"` is content-grounded (asserted values were verified against retrieved source; ≥1 citation is source-backed). Cite it directly. `quotes` entries `{path, lines, quote}` are verbatim live source — quote them instead of re-reading.
+- Reading code: `get_context` skeleton first (~37% of a full Read), then `get_symbol` for bodies, `"path.py:a-b"` range reads for anything between symbols. Raw `Read` is for files the index marks `mostly_full` or cannot serve.
+- The **only** re-read triggers: `bounds: "approximate"`, `_meta.stale_warning`, `search_method: "bm25"`, or `confidence: "low"`/`retrieval_quality: "weak"`.
+- Disallowed rationalizations for extra reads: "just to be safe", "to double-check the tool", "to see the full context" (use the skeleton / a range read), "the file might have changed" (that is what `verified` already checked).
+
+**Composition tips:**
+- `get_answer` → if `confidence` is `medium`/`low`, follow `best_guesses[0].file` or `fallback_targets[0]` into `get_context`, then `get_symbol` for bytes.
+- `get_context` returns `decision_records` titles → `get_why(targets=[...])` for the rationale; `hotspot: true` → `get_risk` before editing.
+- PR review → `get_risk(targets=[...], changed_files=[...])`; read the `directive` block first.
+- A `tombstone` error means the file was deleted/renamed since indexing — follow `successor_paths`.
+
+### Output Distillation
+
+- Prefer `repowise distill <cmd>` for noisy commands — test runs, builds, `git status`/`log`/`diff`, searches, file listings. It runs the command unchanged (exit code preserved) and prints a compact, errors-first rendering; every error line survives.
+- Output may contain a marker like `[repowise#a1b2c3d4e5f6: 230 lines omitted (~6.1k tokens); restore: repowise expand a1b2c3d4e5f6]`. The omitted content is fully preserved — run `repowise expand <ref>` to retrieve it, or `repowise expand <ref> -q <regex>` for just the matching lines.
+- Never re-run a command to see omitted output; expand the marker instead.
+- For structure-level questions about a large indexed file ("what's in here", "which function handles X"), `get_context(["path"], include=["skeleton"])` returns the file with bodies elided — every signature plus the bodies of the most central symbols — at a fraction of the cost of a full Read.
+
+### Codebase Conventions
+**Commands:**
+- Test: `pytest`
+- Lint: `ruff check .`
+- Typecheck: `mypy .`
+
+<!-- REPOWISE:END -->

.pytest_cache/v/cache/lastfailed

@@ -0,0 +1,6 @@
+{
+  "tests/test_hypothesis.py::test_chaos_db_locked_graceful": true,
+  "tests/test_importance_scheduler.py::test_scheduler_rescores_big_delta": true,
+  "tests/test_importance_scheduler.py::test_scheduler_skips_small_delta": true,
+  "tests/test_importance_scheduler.py::test_scheduler_retrieval_signal_boosts": true
+}