fix: guard PR comment updates against stale concurrent writes

[kitsuyui]

Summary

• re-read the managed PR comment before update and delete operations
• skip stale mutations when a newer run already changed the managed comment body
• add focused race regression tests and rebuild dist/**

Why

Older overlapping action runs could delete or overwrite the current managed PR comment after a newer run had already produced the correct final state.
This keeps the existing duplicate-create cleanup while avoiding stale write races on the user-visible comment path.

Verification

• bun run lint

• bun run test

• bun run build

Notes

• dist/** was rebuilt to keep the published action artifact in sync.
• Build completes with the existing ajv/fast-uri warning from upstream type exports.

[github-actions]

🎉 Happy commit!

• dogfooding: PR fix: guard PR comment updates against stale concurrent writes #854 always celebrates.
• dogfooding: af0741e54a38a2175f92195c1ed31626739f458e always celebrates.

[github-actions]

gh-counter

PR gate

	Removed	Added	+/-
TODO/FIXME	0	0	0

Repo dashboard

	main (c70b583)	#854 (64e8d56)	+/-
TODO/FIXME	0	0	0

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Reported by gh-counter

[github-actions]

Code Metrics Report

	main (c70b583)	#854 (64e8d56)	+/-
Coverage	97.6%	97.1%	-0.5%
Code to Test Ratio	1:1.6	1:1.5	-0.1
Test Execution Time	1s	2s	+1s

Details

  |                     | main (c70b583) | #854 (64e8d56) |  +/-  |
  |---------------------|----------------|----------------|-------|
- | Coverage            |          97.6% |          97.1% | -0.5% |
  |   Files             |              7 |              7 |     0 |
  |   Lines             |            170 |            177 |    +7 |
+ |   Covered           |            166 |            172 |    +6 |
- | Code to Test Ratio  |          1:1.6 |          1:1.5 |  -0.1 |
  |   Code              |            714 |            780 |   +66 |
+ |   Test              |           1180 |           1241 |   +61 |
- | Test Execution Time |             1s |             2s |   +1s |

Code coverage of files in pull request scope (100.0% → 98.3%)

Files	Coverage	+/-	Status
src/github.ts	98.3%	-1.7%	modified

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Reported by octocov

[github-actions]

gh-build-size

Target	main	#854	+/-
Total action artifacts	23,300,626 B	23,303,031 B	+2,405 B
Runtime bundle	1,153,666 B	1,153,987 B	+321 B
Source maps	17,130,935 B	17,133,019 B	+2,084 B

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Reported by gh-build-size