fix(miner): close_pr runs unconditionally before its best-effort comment

[JSONbored]

Summary

Follow-up to #4848/#5480, addressing a real nit gittensory's own review caught after that PR was already merged.

buildClosePrSpec (packages/gittensory-engine/src/miner/local-write-tools.ts) chained gh pr comment && gh pr close -- if gh pr comment failed (e.g. a transient network blip), the && meant gh pr close never ran, silently leaving a known-losing PR open. That's the exact outcome claim-conflict resolution exists to prevent.

The close now runs first and unconditionally; the explanatory comment is a best-effort follow-up that only runs once the close itself succeeds, and can never block or mask it.

Also documents (in claim-conflict-resolver.js) why assembleCompetingClaims deliberately excludes same-author PRs -- a miner never competes against its own retry attempts, per the same reviewer nit.

Test plan

• tsc --noEmit --incremental false clean
• npx vitest run test/unit test/contract -- 774/775 passing (1 pre-existing unrelated skip)
• Per-file patch coverage verified: 100% on every changed line in local-write-tools.ts and claim-conflict-resolver.js
• npm run docs:drift-check / manifest:drift-check / engine-parity:drift-check all clean
• npm audit --audit-level=moderate -- 0 vulnerabilities
• git diff --check clean

[superagent-security]

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

[cloudflare-workers-and-pages]

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	gittensory-ui	446c279	Commit Preview URL Branch Preview URL	Jul 12 2026, 11:10 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.74%. Comparing base (f0426b5) to head (446c279).
⚠️ Report is 6 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5494   +/-   ##
=======================================
  Coverage   94.74%   94.74%           
=======================================
  Files         563      563           
  Lines       44823    44823           
  Branches    14669    14669           
=======================================
  Hits        42467    42467           
  Misses       1621     1621           
  Partials      735      735           

Flag	Coverage Δ
shard-1	44.34% <ø> (ø)
shard-2	35.38% <ø> (ø)
shard-3	31.95% <ø> (ø)
shard-4	31.38% <ø> (ø)
shard-5	33.19% <ø> (-0.01%)	⬇️
shard-6	43.56% <ø> (ø)

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

Files with missing lines	Coverage Δ
...s/gittensory-engine/src/miner/local-write-tools.ts	100.00% <ø> (ø)
...es/gittensory-miner/lib/claim-conflict-resolver.js	100.00% <ø> (ø)

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