fix(miner): refuse a duplicate attempt when this miner already has an open PR for the exact issue

[JSONbored]

Summary

AMS audit fix (#8808): a crash between PR-open and the attempt's finally left an orphaned open PR that nothing downstream would ever treat as a conflict — claim-conflict resolution deliberately exempts the miner's own PRs, freshness excludes same-author PRs, and the issue-tagged own-submissions ledger was never consulted — so a retry double-opened.

Changes

• rejection-signal.ts — resolveOwnOpenPrForIssue(repo, issue): issue-matched own submissions → bounded live PR-state checks (same maxRejectionHistoryChecks fan-out cap) → first still-OPEN PR number, else null. Fully fail-open (store read failure, fetch rejection, degenerate inputs → null): an idempotency guard must never block a legitimate attempt on a hiccup. A closed/merged prior PR never blocks. Shared option plumbing extracted into resolveHistoryOptions (reused by the Check a miner's own prior-rejection history on a repo (rejectionSignaled's second documented trigger) #5655 sibling — no duplicated arms).
• attempt-cli.ts — refuses before a worktree slot is consumed, mirroring the rejection-signal block: attempt_aborted/attempt_blocked events + blocked_own_open_pr result naming the existing PR, exit 5, injection seam mirroring resolveRejectionSignaled. Refuse—not adopt: the still-open PR is already doing this issue's job.

Test plan

• npm run typecheck clean; @loopover/miner builds
• 6 resolver tests (open-PR hit, issue-mismatch no-fetch, closed-doesn't-block, both fail-open arms, fan-out bound + degenerate inputs + non-array guard) and 3 attempt-cli wiring tests (refusal before allocator.acquire, JSON + stderr shapes, null-proceeds)
• 135 tests green across both suites
• Every changed line (script-verified against the diff): 0 uncovered statements/branches

Closes #8808

[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 92.27%. Comparing base (11fb8ee) to head (eae5e2d).
⚠️ Report is 7 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8815      +/-   ##
==========================================
- Coverage   93.81%   92.27%   -1.55%     
==========================================
  Files         797      797              
  Lines       79608    79635      +27     
  Branches    24127    24136       +9     
==========================================
- Hits        74686    73484    -1202     
- Misses       3556     5090    +1534     
+ Partials     1366     1061     -305     

Flag	Coverage Δ
backend	92.95% <100.00%> (-2.15%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
packages/loopover-miner/lib/attempt-cli.ts	100.00% <100.00%> (ø)
packages/loopover-miner/lib/rejection-signal.ts	98.95% <100.00%> (+0.20%)	⬆️

... and 2 files with indirect coverage changes

[loopover-orb]

Important

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_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed · 🟪 Reviewing}