feat(hook): add Codex command rewriting

[paranoa233]

Summary

• add a native rtk hook codex processor for Codex PreToolUse payloads
• install the hook in global or project hooks.json without overwriting existing hooks
• make installation idempotent, remove only RTK's entry on uninstall, and report hook status
• update Codex integration and hook architecture documentation

Why

Codex currently receives prompt-level RTK guidance but cannot transparently rewrite supported shell commands. This adds the same automatic path while using Codex's native updatedInput.command protocol.

Impact

• unsupported, malformed, or non-Bash payloads emit no output and remain non-blocking
• rewritten input preserves other tool_input fields
• accepting the rewrite does not replace Codex's normal sandbox and approval checks
• existing user hook configuration is preserved

Test plan

• cargo fmt --all --check
• cargo clippy --all-targets
• cargo test (2,447 unit tests plus integration suites)
• manual stdin smoke test for rewrite and pass-through behavior

Part of #2921. Paired with #2926.

[CLAassistant]

All committers have signed the CLA.

[KuSh]

Closing in favour of #3552, which covers the same Codex PreToolUse integration, is the version a collaborator has reviewed, and uses the transparent updatedInput path that Codex now applies end to end. Thanks for the work here. Please take anything your branch handles that #3552 misses to that thread so the effort stays in one place.