fix: change stop hook from blocking to warning to prevent auto-commits (microsoft#1451)

## Summary

Changes the stop hook from `"decision": "block"` to `"decision": "warn"`
so the agent asks the user before committing instead of auto-committing.

## Background

The `stop_hook.py` is a pre-session stop hook that runs when an agent
(maintainer) session ends. It checks the git state for:

1. **Uncommitted TypeScript changes** (staged, modified, or untracked
`.ts`/`.tsx` files) — reminds the agent to run pre-commit checks (lint,
type-check, tests)
2. **Staged but uncommitted changes** — reminds the agent that work
hasn't been committed

## Problem

Previously, both checks used `"decision": "block"`, which **prevented
the agent from ending the session** until the condition was resolved.
The reason text explicitly told the agent to commit changes (e.g., *"If
checks pass and changes are ready, commit them"*). This combination
caused the agent to **auto-commit every time** without asking the user,
which is undesirable when the user wants to review changes before
committing.

## Changes

- **`"decision": "block"` → `"decision": "warn"`** for both the TS
changes check and the staged changes check. The agent sees the warning
but is no longer forced to act on it.
- **Removed commit instructions** from the reason text (e.g., *"commit
them"*, *"Either commit them with a proper message"*) so the agent
doesn't interpret them as required actions.
- **Added explicit user-consent escape**: reason text now says *"Ask the
user whether to commit or leave changes uncommitted"*, ensuring the
agent defers to the user.

## Files Changed

- `.github/hooks/scripts/stop_hook.py`

Author: StellaHuang95

.github/hooks/scripts/stop_hook.py

@@ -110,13 +110,12 @@ def main() -> int:
         response = {
             "hookSpecificOutput": {
                 "hookEventName": "Stop",
-                "decision": "block",
+                "decision": "warn",
                 "reason": (
                     "You have uncommitted TypeScript changes. "
-                    "Before finishing, use the run-pre-commit-checks skill "
+                    "Before finishing, consider using the run-pre-commit-checks skill "
                     "or manually run: npm run lint && npm run compile-tests && npm run unittest. "
-                    "If checks pass and changes are ready, commit them. "
-                    "If this session is just research/exploration, you can proceed without committing."
+                    "Ask the user whether to commit or leave changes uncommitted."
                 ),
             }
         }
@@ -128,10 +127,10 @@ def main() -> int:
         response = {
             "hookSpecificOutput": {
                 "hookEventName": "Stop",
-                "decision": "block",
+                "decision": "warn",
                 "reason": (
                     "You have staged changes that haven't been committed. "
-                    "Either commit them with a proper message or unstage them before finishing."
+                    "Ask the user whether to commit them or leave them staged."
                 ),
             }
         }