feat(scoring): wire contributor validity floors into score preview (#808)

[bohdansolovie]

Summary

Completes the remaining #808 contributor validity floors by wiring upstream eligibility gates into score preview:

• Merged PR history floor (MIN_VALID_MERGED_PRS): zeroes the estimate when repo-level merged count is known and below the floor; inferred from contributor evidence when omitted.
• Issue-discovery validity floor (MIN_VALID_SOLVED_ISSUES, MIN_ISSUE_CREDIBILITY): applied when issue-discovery is relevant (non-zero issueDiscoveryShare or linked-issue mode); skipped when history is unknown.
• Local branch analysis now passes mergedPullRequests, validSolvedIssues, and issueCredibility from outcome history.
• Scenario previews (cleanGates, afterPendingMerges, bestReasonableCase) project history cleanup; gate deltas and public blocker text updated.

Fixes #808 (partial — completes contributor validity wiring alongside prior open-issue spam and test-file weight work).

Test plan

• npm run test:ci (or targeted test/unit/scoring.test.ts + test/unit/local-branch.test.ts)
• Merged floor: at floor passes, below floor blocks with merged_pr_history_floor
• Unknown merged count does not block
• Evidence inference for merged count
• Issue-discovery floor blocks when relevant and below floors
• Issue-discovery floor skipped when not relevant or history unknown
• bestReasonableCase and afterPendingMerges scenario projections

[superagent-security]

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.41%. Comparing base (823749a) to head (69b91f0).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1284   +/-   ##
=======================================
  Coverage   95.40%   95.41%           
=======================================
  Files         193      193           
  Lines       20973    21006   +33     
  Branches     7581     7609   +28     
=======================================
+ Hits        20010    20043   +33     
  Misses        383      383           
  Partials      580      580           

Files with missing lines	Coverage Δ
src/api/routes.ts	94.60% <ø> (ø)
src/openapi/schemas.ts	100.00% <ø> (ø)
src/scenarios/scenario-summary.ts	100.00% <ø> (ø)
src/scoring/preview.ts	99.02% <100.00%> (+0.10%)	⬆️
src/signals/local-branch.ts	97.20% <100.00%> (+0.02%)	⬆️

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[bohdansolovie]

@JSONbored
Could you continue review please?
Thank you for your work

[JSONbored]

@JSONbored Could you continue review please? Thank you for your work

Please note, if you comment/message for reviews in the future, it's a +5 day wait to get reviewed. Too many people keep bugging me to review - I know the PRs need to be reviewed and I'll review them when time permits :)

[JSONbored]

Confirmed net-new on current main — #835 wired the issue-discovery constants into the engine; this closes the preview-side gap so a miner's projection actually reflects the validity floors. Conservative "unknown ⇒ don't gate" semantics, mirrored as blocker + gate-delta + scenario, OpenAPI regenerated. On the active preview-accuracy line, real value, low maintenance. Merge. (Minor: it links the now-closed #808; the work itself is the legitimate follow-up.)