fix(db): drop stale migration-90 grandfather entry

[joaovictor91123]

Summary

• Drop the stale 0090 entry from KNOWN_MIGRATION_DUPLICATES — 0090_pull_request_detail_sync_head_sha was renumbered to 0092, so only 0090_contributor_cap_label remains on disk.
• Update check-migrations header comment + collision unit coverage for the single remaining 90 file.
• Fix the success-summary assertion in check-migrations-script.test.ts (4 grandfathered duplicates, not 5) — this was the CI failure on fix(db): drop stale migration-90 grandfather entry #8916.

Closes #8897

Scope

• The PR title follows type(scope): short summary Conventional Commit format, for example fix(api): restore profile access checks.
• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked a currently open issue this PR resolves (e.g. Closes #123) — a linked open issue is required for every contributor PR.

Validation

• git diff --check
• npm run actionlint
• npm run typecheck
• npm run test:coverage locally; codecov/patch requires ≥99% coverage of the lines AND branches you changed (aim for 100% on your diff so CI variance does not fail near the threshold). Global coverage is a non-blocking trend with a loose 90% backstop, not the gate.
• npm run test:workers
• npm run build:mcp
• npm run test:mcp-pack
• npm run ui:openapi:check
• npm run ui:lint
• npm run ui:typecheck
• npm run ui:build
• npm audit --audit-level=moderate
• New or changed behavior has unit/integration tests for new branches, fallback paths, and sanitizer boundaries

If any required check was skipped, explain why:

• Full suite / typecheck / UI / MCP not re-run locally (Node 24 vs engines Node 22). Change is confined to migration grandfather list + unit tests; CI is source of truth. Replaces fix(db): drop stale migration-90 grandfather entry #8916 which failed solely on check-migrations-script.test.ts expecting the removed 0090 grandfather entry.

Safety

• No secrets, wallet details, hotkeys, coldkeys, user PATs, private keys, raw trust scores, private rankings, or private maintainer evidence are exposed.
• Public GitHub text stays sanitized, low-noise, and does not imply compensation guarantees or optimization tactics.
• Auth, cookie, CORS, GitHub App, Cloudflare, or session changes include negative-path tests.
• API/OpenAPI/MCP behavior is updated and tested where needed.
• UI changes use live API data or real empty/error/loading states, not production mock/demo fallbacks.
• Visible UI changes include a UI Evidence section below with JPG/JPEG or PNG screenshots arranged as organized, captioned, clickable thumbnails. SVG screenshots are not used as review evidence. Review-only screenshots or recordings are not committed to the repository.
• Public docs/changelogs are updated where needed; changelogs are only edited for release-prep PRs.

UI Evidence

N/A — no visible UI changes.

Notes

• Replacement for fix(db): drop stale migration-90 grandfather entry #8916 (same fix + the missing summary-test update that failed validate-tests).

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
21889	1	21888	21

View the top 1 failed test(s) by shortest run time

test/unit/miner-worktree-allocator-collisions.test.ts > loopover-miner worktree allocator collisions (#4298) > rejects excess simultaneous cross-process acquire calls at the concurrency cap

Stack Traces | 0.785s run time

AssertionError: expected [ …(3) ] to have a length of 2 but got 3

- Expected
+ Received

- 2
+ 3

 ❯ test/unit/miner-worktree-allocator-collisions.test.ts:162:23

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[joaovictor91123]

Closing to re-open on latest main after validate-tests failed on an unrelated flake (miner-worktree-allocator-collisions concurrency cap race - expected 2 fulfilled acquires, got 3). Our migration-grandfather assertion passed; one-shot policy forbids a follow-up push.