chore: import upstream snapshot with attribution

hooks/codex/README.md

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+# Codex CLI Hooks
+
+> Part of [`hooks/`](../README.md) — see also [`src/hooks/`](../../src/hooks/README.md) for installation code
+
+## Specifics
+
+- Prompt-level guidance via awareness document -- no programmatic hook
+- `rtk-awareness.md` is injected into `AGENTS.md` with an `@RTK.md` reference
+- Installed to `$CODEX_HOME` when set, otherwise `~/.codex/`, by `rtk init --codex`

hooks/codex/rtk-awareness.md

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+# RTK - Rust Token Killer (Codex CLI)
+
+**Usage**: Token-optimized CLI proxy for shell commands.
+
+## Rule
+
+Always prefix shell commands with `rtk`.
+
+Examples:
+
+```bash
+rtk git status
+rtk cargo test
+rtk npm run build
+rtk pytest -q
+```
+
+## Meta Commands
+
+```bash
+rtk gain            # Token savings analytics
+rtk gain --history  # Recent command savings history
+rtk proxy <cmd>     # Run raw command without filtering
+```
+
+## Verification
+
+```bash
+rtk --version
+rtk gain
+which rtk
+```