fix(jangar): bound postgres pool usage

[gregkonush]

Summary

• Bounds shared Jangar DATABASE_URL Postgres pools to 4 connections per process by default.
• Bounds memory-provider Postgres pools to 2 connections per connection string by default.
• Adds environment-backed pool-size defaults and regression coverage for shared storage and memory-provider pool sizing.

Related Issues

None

Testing

• bun install --frozen-lockfile --ignore-scripts - pass
• bunx oxfmt --check services/jangar/src/server/storage-config.ts services/jangar/src/server/db.ts services/jangar/src/server/memory-provider.ts services/jangar/src/server/__tests__/storage-config.test.ts services/jangar/src/server/__tests__/memory-provider.test.ts - pass
• bun run --cwd services/jangar lint - pass
• bun run --cwd services/jangar lint:oxlint - pass with existing warnings and 0 errors
• bun run --cwd services/jangar lint:oxlint:type - pass with existing warnings and 0 errors
• bun run --cwd services/jangar test -- src/server/__tests__/storage-config.test.ts src/server/__tests__/memory-provider.test.ts src/server/__tests__/db.test.ts - pass
• cd services/jangar && bunx tsc --noEmit --project tsconfig.paths.json && bun run docs:inventory:check && bun run check:module-sizes - pass
• bun run --cwd services/jangar build - pass
• gh pr checks 5559 -R proompteng/lab --watch - pass/skipped only

Screenshots (if applicable)

N/A

Breaking Changes

None

Checklist

• Testing section documents the exact validation performed (or N/A with justification).
• Screenshots and Breaking Changes sections are handled appropriately (removed or filled in).
• Documentation, release notes, and follow-ups are updated or tracked.

[gregkonush]

Marco release update as of 2026-05-05T20:48Z:

• Gate: merge-ready for fix(jangar): bound postgres pool usage #5559. GitHub reports mergeStateStatus=CLEAN, draft=false, one commit b7151aa, 49 additions and 4 deletions across 5 files.
• Required checks are pass/skipped only: changed-file routing, semantic title, semantic commits, jangar-ci / lint-and-typecheck / run, agents-ci / validate, and agents-ci / integration.
• Local validation is green: frozen install, targeted oxfmt, Jangar lint, Oxlint, type-aware Oxlint, targeted pool Vitest, tsc --noEmit plus docs inventory and module-size guardrail, and Jangar build all passed. Oxlint warnings are existing warnings with 0 errors.
• PR body was corrected before merge to remove a stale image-promotion bullet that is not in the current diff.
• Decision: squash-merge fix(jangar): bound postgres pool usage #5559 now, then verify GitOps/cluster rollout health for Jangar and agents workloads. Rollback path if rollout is unhealthy: revert the fix(jangar): bound postgres pool usage #5559 squash commit on main and let GitOps reconcile the previous Jangar code/image path.