[codex] Inject LSP diagnostics context

[code-yeongyu]

Summary

• Mirror PostToolUse LSP diagnostic failures into hookSpecificOutput.additionalContext.
• Keep the existing decision: "block" feedback path so Codex still fixes the edited file immediately.
• Add hook tests for the modern Codex output shape, multi-file filtering, and failed mutation short-circuit behavior.
• Update built dist artifacts and README behavior docs.

Why

Codex now records PostToolUse additionalContext into model-visible conversation context. The LSP hook already blocked on diagnostics, but it did not use the context injection path that Codex, omo, and opencode-style post-tool integrations rely on for automatic follow-up behavior.

Validation

• npm ci
• npm test -- test/codex-hook.test.ts first failed before implementation, then passed after the fix
• npm test
• npm run check
• bun --install=fallback /Users/yeongyu/.agents/skills/typescript-programmer/scripts/check-no-excuse-rules.ts src/codex-hook.ts test/codex-hook.test.ts
• LSP diagnostics on changed TypeScript files
• npm pack --dry-run
• tmux hook CLI smoke: node dist/cli.js hook post-tool-use < test/fixtures/post-tool-use.json
• tmux MCP smoke: printf '%s\n' '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | node dist/cli.js mcp

Review

• External gpt-5.5 xhigh expert review approved the diff with no blocking findings or required missing tests.

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Summary by cubic

Inject LSP diagnostics into PostToolUse hook output so Codex sees the same errors it blocks on and can auto-fix edits. Keeps decision: "block" behavior and adds tests for multi-file and failed mutation cases.

• New Features
  • Mirrors diagnostic failures into hookSpecificOutput.additionalContext with hookEventName: "PostToolUse".
  • Includes only files with errors; skips clean files and unsupported extensions.
  • Short-circuits when a mutation tool fails (no diagnostics run). Tests cover new output shape, multi-file filtering, and failure short-circuit; README updated.

^{Written for commit a6e63cb. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

No issues found across 6 files

_{Re-trigger cubic}