feat(scoring): validate linked issue multiplier eligibility

[grnlemon]

Summary

• Closes feat(scoring): reconcile linked-issue multipliers with solved_by_pr truth #91.
• Add solved-by-PR linkage state to issue quality records and scoring preview inputs.
• Require validated solved-by-PR evidence before applying the standard linked-issue multiplier.
• Prefer official/mirror issue data when available, preserve public hygiene guidance, and keep multiplier reasoning private.

Scope

• 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 an issue, or this is small enough that the summary explains why an issue is not needed.

Validation

• git diff --check
• npm run actionlint
• npm run typecheck
• npm run test:coverage
• 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
• Coverage remains at or above 97% for statements, branches, functions, and lines.

If any required check was skipped, explain why:

• None. npm run test:ci passed locally. Coverage summary: statements 98.95%, branches 97%, functions 97.83%, lines 99.5%.

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. N/A: no auth, cookie, CORS, GitHub App, Cloudflare, or session changes.
• 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. N/A: no UI runtime changes.
• Visible UI changes include screenshots or a short recording. N/A: no visible UI changes.
• Public docs/changelogs are updated where needed; changelogs are only edited for release-prep PRs.

Notes

• Public packets continue to expose linked-issue hygiene guidance only; private score preview/MCP responses carry multiplier eligibility reasoning.
• Mirror issue state is preferred for linked issue eligibility when available, with caution surfaced when mirror data is unavailable.

[JSONbored]

@MkDev11 This is ready from my side. Linked-issue multiplier eligibility is wired through scoring preview, local branch analysis, API/MCP/OpenAPI surfaces, and focused tests. The implementation keeps the multiplier tied to eligible linkage instead of treating any issue reference as scoreable. Current checks are green and the merge tree is clean.