[codex] Harden issue workflow skills

[kmatsunami]

Summary

• Add stricter guardrails to gh-issue-resolver for stale issue reviews, broad scope terms, review thread inventory, and bounded gate fallback.
• Add prompt/template examples for capability matrices and timeout fallback packets.
• Allow configured GitHub write tools in .codex/config.toml and ignore local .claude/ worktree artifacts.

Impact

• Makes issue-to-PR automation less likely to proceed from stale or under-specified issue scope.
• Keeps local Claude worktree artifacts out of Git status without committing generated files.

Validation

• git diff --check origin/main...HEAD
• GitHub compare verified main...codex/issue-approval-loop-hardening is ahead 2 / behind 0.

No linked issue.