docs: document RTK runtime and output boundaries

CHANGELOG.md

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+# Changelog
+
+This changelog records user-visible RTK Codex Plugin releases.
+
+## [Unreleased]
+
+## [0.1.0] - 2026-07-25
+
+### Included
+
+- PreToolUse classification for supported shell command payloads;
+- optional `rtk rewrite <command>` integration with bounded validation and
+  fail-open behavior;
+- pre-execution guarding for recognized long-line inspection shapes;
+- PostToolUse byte, line, and best-effort aggregate-turn budgets;
+- local artifact preservation for qualifying guarded or compacted output;
+- stream, parallel-tool, wrapper, bypass, and Pitlane pass-through handling;
+- standard-library test coverage for the public behavior surface.
+
+### Documentation
+
+- added architecture, decision-flow, sequence, and state-lifecycle diagrams;
+- documented Python 3.11+ and POSIX requirements;
+- documented native Windows exclusion and WSL2 operation;
+- added pinned release installation, update, rollback, and uninstall guidance;
+- documented every output-budget override and state path;
+- documented artifact sensitivity, permissions, retention, and trust
+  boundaries;
+- added compatibility, troubleshooting, contribution, and security guides.
+
+### Release scope
+
+- POSIX plugin/source tarball;
+- SHA-256 integrity manifest;
+- no bundled RTK executable;
+- no native Windows, PyPI, or npm package;
+- no signed provenance or reproducible-build claim.
+
+[Unreleased]: https://github.com/mmmihaeel/rtk-codex-plugin/compare/v0.1.0...HEAD
+[0.1.0]: https://github.com/mmmihaeel/rtk-codex-plugin/releases/tag/v0.1.0

CONTRIBUTING.md

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+# Contributing
+
+RTK Codex Plugin is intentionally small, but classifier and output-budget
+changes can alter shell behavior. Contributions should be narrow, explicit
+about command semantics, and backed by focused tests.
+
+## Environment
+
+Use Python 3.11+ on Linux, WSL2, or another POSIX environment:
+
+```bash
+python3 --version
+git clone https://github.com/mmmihaeel/rtk-codex-plugin.git
+cd rtk-codex-plugin
+```
+
+The project uses only the Python standard library.
+
+## Run verification
+
+```bash
+python3 -m json.tool .codex-plugin/plugin.json >/dev/null
+python3 -m json.tool hooks/hooks.json >/dev/null
+test -x hooks/rtk-codex-hook
+test -x hooks/rtk-output-guard
+test -x hooks/rtk-output-post-hook
+make test
+```
+
+The public suite discovers 50 tests: 49 pass and one public-projection exporter
+check is intentionally skipped because that exporter is not included here.
+
+## Change expectations
+
+For classifier changes, add cases covering:
+
+- the intended rewrite or guard path;
+- neighboring pass-through and exact-output shapes;
+- wrappers, environment prefixes, quoting, and shell-control boundaries;
+- missing, invalid, or failing external RTK behavior;
+- Pitlane-owned shapes when integration ordering could change.
+
+For PostToolUse changes, cover:
+
+- byte and line thresholds;
+- summary-smaller checks and artifact removal;
+- aggregate turn state;
+- `write_stdin` and parallel payloads;
+- bypass markers;
+- sensitive path and filename handling.
+
+Do not add benchmark, token-saving, security, or cross-runtime claims without
+reproducible evidence.
+
+## Documentation
+
+Update public documentation when a change affects:
+
+- supported Python or platforms;
+- plugin/hook payload contracts;
+- environment variables or default limits;
+- artifact locations, permissions, or retention;
+- bypass behavior;
+- optional RTK interface;
+- ecosystem ordering or compatibility.
+
+All public prose must remain English. Verify Markdown formatting, local links,
+and examples before opening a pull request.
+
+## Pull requests
+
+Describe:
+
+- the user-visible behavior;
+- why the selected classifier boundary is safe enough for its intended role;
+- exact tests run;
+- platform/runtime combinations not tested;
+- security, artifact, or release impact.
+
+Contributions are accepted under the [MIT License](./LICENSE).