docs(miner): document and load-test shared store concurrency model (#4942)

[andriypolanski]

Summary

• The miner's local-store concurrency story was written for two processes on one SQLite file; after Migrate AMS's local-store layer (node:sqlite) to the shared pg-adapter/SqliteDriver seam #7175's shared SqliteDriver seam that model needed an explicit shared-service restatement (Re-evaluate the local concurrency model for a shared-service context #4942).
• This adds the maintainer concurrency-model doc plus a correctness load suite (no lost updates / no double-claim under the patterns the model claims are safe).
• Replaces closed docs(miner): document and load-test shared store concurrency model #8002: splits the load suite into three coverage-hitting test files and imports miner lib/*.ts so each scoped CI shard emits non-empty coverage/lcov.info under --coverage.all=false.

Closes #4942

Change

• Doc packages/loopover-miner/docs/ams-shared-store-concurrency-model.md: what SQLite BEGIN IMMEDIATE / busy_timeout, miner createD1Adapter.batch, and ORB createPgAdapter (READ COMMITTED) guarantee — and what they do not. Contrasts installation-concurrency-admission / mapWithConcurrency. Notes control-plane one-DB-per-tenant isolation.
• Links from operations-runbook.md and ams-storage-abstraction-research.md.
• Load / race tests (split for 3-shard scoped CI):
  • miner-shared-store-concurrency-cap.test.ts — cross-process claimIssueWithinCap (cap=1 → exactly one active row)
  • miner-shared-store-concurrency-adapter.test.ts — 32× concurrent UPDATE … SET n = n + 1 via createD1Adapter.batch; naive RMW pins the documented lost-update non-guarantee; optional Postgres when PG_TEST_URL is set
  • miner-shared-store-concurrency-doc.test.ts — doc assertions + local-store smoke open
  • miner-operations-runbook.test.ts — also opens a local store so a shard that only selects it still produces lcov

Validation

• git diff --check clean.
• Targeted vitest green (PG case skipped without PG_TEST_URL).
• With build:miner present, adapter suite coverage hits local-store.ts / store-db-adapter.ts in coverage/lcov.info.
• Docs / fixtures / unit tests only — Codecov patch has no graded production-diff lines.

UI Evidence

N/A — documentation + concurrency correctness tests only.

Made with Cursor

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[loopover-orb]

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