fix(jangar): index torghut quant health lookup

[gregkonush]

Summary

• Adds a registered Jangar migration for the Torghut quant pipeline health account/window/latest lookup index.
• Rewrites the latest-stage query to use an account/window-scoped DISTINCT ON plan instead of a window-function scan over quant_pipeline_health.
• Adds focused regression coverage for migration registration and the indexable scoped SQL shape.

Related Issues

None

Testing

• PASS: bun run --cwd services/jangar pretest
• PASS: bunx oxfmt --check src/server/torghut-quant-metrics-store.ts src/server/__tests__/torghut-quant-metrics-store.test.ts src/server/__tests__/kysely-migrations.test.ts src/server/kysely-migrations.ts src/server/migrations/20260505_torghut_quant_pipeline_health_window_index.ts from services/jangar
• PASS: bunx vitest run --config vitest.config.ts src/server/__tests__/kysely-migrations.test.ts src/server/__tests__/torghut-quant-metrics-store.test.ts src/routes/api/torghut/trading/control-plane/quant/-health.test.ts from services/jangar
• PASS: bunx tsc --noEmit -p tsconfig.app.json --pretty false from services/jangar
• PASS: bun run --filter @proompteng/jangar lint
• PASS: bun run --filter @proompteng/jangar lint:oxlint (0 errors; existing unrelated warnings remain)
• PASS: bun run --filter @proompteng/jangar lint:oxlint:type (0 errors; existing unrelated warnings remain)
• PASS: git diff --check origin/main...HEAD

Screenshots (if applicable)

N/A

Breaking Changes

Adds a non-concurrent Kysely migration for torghut_control_plane.quant_pipeline_health; production is being repaired manually with the same index created concurrently before this migration rolls out.

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]

Merge and rollout gate: green and closed with one residual restart noted.

Evidence as of 2026-05-05T22:27Z:

• PR fix(jangar): index torghut quant health lookup #5570 merged at 49e27b93b72038f9a3a4bee28d9e8e0d041543a3 after all PR checks were pass/skipped and review threads were empty.
• Source-commit post-merge workflows are green: jangar-build-push, jangar-release, agents-ci, and Docker Build and Push all completed successfully for 49e27b93.
• GitOps promotion PR chore(jangar): promote image 49e27b93 #5574 merged at dd5ca99046541415e04908e4ac675424558297e6; release PR checks are pass/skipped only, including Jangar CI, argo-lint, and kubeconform.
• jangar-post-deploy-verify passed: Argo sync Synced, health Healthy, revision and desired revision both dd5ca99046541415e04908e4ac675424558297e6.
• Live pod evidence: jangar-ff5f988cd-rs2rp is Running with both containers ready on registry.ide-newton.ts.net/lab/jangar:49e27b93@sha256:9a28668ea8b1b63ee9afa3e1ae99dac5fb602b606740e524f38b8ed9cb31775a.
• Residual risk: the Jangar app container restarted once after verifier success with previous logs showing PostgreSQL heartbeat connection termination. A 90-second stability check kept it ready at app ready=true restarts=1; recent logs were quiet.