add confirm-destructive, git-checkpoint, notify extensions

README.md

@@ -109,7 +109,57 @@ The status bar shows `⚡ own master` or `⚡ system master` so you can see whic
 
 ---
 
-## Adding a new extension
+### `confirm-destructive.ts`
+
+Confirmation gates for dangerous bash commands and destructive session actions. Always-on — no flag needed.
+
+**Bash commands intercepted:**
+- Recursive removes (`rm -rf`, `rm -r`, etc.)
+- Any `sudo` command
+- `chmod`/`chown 777`
+- `dd if=` (disk operations)
+- `mkfs` (format filesystem)
+- `git push --force` / `git push -f`
+- Writes to `/dev/*`
+- `truncate --size 0`
+
+In non-interactive mode (e.g. `pi -p`) dangerous commands are blocked outright rather than prompted.
+
+**Session actions gated:**
+- `/new` — confirms before clearing the session
+- `/resume` — confirms before switching away if the current session has messages
+- `/fork` — always confirms
+
+---
+
+### `git-checkpoint.ts`
+
+Creates a git stash checkpoint at the start of each turn, keyed to the session entry ID. If you `/fork` from a past entry, you're offered the option to restore the code to that point.
+
+Silently skips when the working directory isn't inside a git repo, or when there are no changes to stash. Status bar shows `⎇ N checkpoints` during active sessions.
+
+**Notes:**
+- Uses `git stash create` — non-destructive, doesn't touch your working tree
+- Stash objects persist in the git repo even after pi exits, so you can apply them manually with `git stash apply <ref>` if needed
+- Checkpoints are in-memory per session — the entry→ref mapping is lost on restart, but the underlying stash objects remain
+
+---
+
+### `notify.ts`
+
+Sends a native terminal notification when the agent finishes and is waiting for input. Only fires when the agent ran for longer than the threshold (default 8 seconds) — quick responses are silently skipped.
+
+**Terminal support:**
+- Kitty (`KITTY_WINDOW_ID`) → OSC 99
+- Windows Terminal / WSL (`WT_SESSION`) → Windows toast
+- Everything else (iTerm2, WezTerm, Ghostty) → OSC 777
+
+**Flag:**
+
+```bash
+pi --notify-min-secs 15   # only notify for tasks over 15 seconds
+pi --notify-min-secs 0    # notify on every agent completion
+```
 
 1. Drop a `.ts` file into `extensions/`
 2. Re-run `./install.sh` — it picks up the new file and symlinks it