Add a fallback when fork tokens cannot post comments

[Pybsama]

Summary

• catch the known Resource not accessible by integration error when a fork workflow token cannot create or update a comment
• emit a GitHub warning and log the complete comment that would have been posted
• add the same message to the Actions Job Summary when it is available
• preserve the original exit code and stderr for every other command failure
• route all seven PR, Issue, and Discussion create/update paths through the fallback
• make top-level Discussion comments use the helper's explicit ID and message arguments

Fixes #44.

Testing

• added Bash subprocess tests for success, the known fork permission error, unexpected failures, multiline argument preservation, and top-level Discussion parameters
• confirmed the fallback tests fail against the previous implementation before the helper exists
• npm ci && npm test — 10 tests passed
• focused test file repeated 20 times
• bash -n queries.sh
• parsed action.yml with js-yaml
• git diff --check

[Pybsama]

Fresh current-main validation update:

• PR head 8645d27afd80b2bc471de85bc57826d81a436d9c is ahead 1 / behind 8 relative to current main 9984e213ae846b8c2342d393085e2483a615f8db. The eight upstream commits only change package.json and package-lock.json; a merge-tree simulation is conflict-free and produces tree f9a1824e1b5a53074f9fbf1000043784db8bb162.
• On that exact merge-equivalent tree, lockfile installation and the complete Vitest suite passed 10/10 on Node 24.11.1 and Node 20.19.5. The Node 24 suite also passed 20 consecutive full-suite repetitions.
• bash -n queries.sh passed. action.yml, the CI workflow, and the self-test workflow all parse with the current pinned js-yaml. Target-file and staged diff checks pass.
• No equivalent implementation is present on current main or in another PR.
• The existing CI and Test Accessibility-alt-text-bot runs are both action_required with zero jobs, so they are waiting for maintainer approval rather than reporting test failures.
• Prior independent review found no remaining blocking issue. The original head remains mergeable, so I have not rewritten it solely for dependency-only drift. Ready for review.