Keep the git hook rebuild root inside the repo

Team setup documents committing the graphify output directory, and
.graphify_root lives inside it, so its contents are checkout
controlled. Both generated git hooks read that file and pass its
value straight to _rebuild_code with no bound, so a value planted
there by a forked PR could point the rebuild, and therefore what it
reads and what it writes back into that same committed directory, at
a location outside the repository the hook runs in. Both rebuild
bodies now only adopt the saved root when it resolves inside the
working tree the hook is running from, falling back to the repo top
otherwise. Fixes #3265.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017qfdzgbA5KedGEjD1AayNh
(cherry picked from commit 31aa4d4e9d)

graphify/hooks.py

@@ -188,7 +188,17 @@ try:
     if _saved.exists():
         _txt = _saved.read_text(encoding='utf-8-sig').strip()
         if _txt:
-            _root = Path(_txt)
+            _candidate = Path(_txt)
+            try:
+                _cwd = Path.cwd().resolve()
+                _resolved = _candidate.resolve()
+                _in_repo = _resolved == _cwd or _cwd in _resolved.parents
+            except OSError:
+                _in_repo = False
+            if _in_repo:
+                _root = _candidate
+            else:
+                print(f'[graphify hook] ignoring out-of-repo .graphify_root: {_txt}')
     _rebuild_code(_root, changed_paths=changed, force=_force)
     # Refresh the work-memory lessons doc when saved Q&A outcomes exist
     # (best-effort; never fails the hook).
@@ -250,7 +260,17 @@ try:
     if _saved.exists():
         _txt = _saved.read_text(encoding='utf-8-sig').strip()
         if _txt:
-            _root = Path(_txt)
+            _candidate = Path(_txt)
+            try:
+                _cwd = Path.cwd().resolve()
+                _resolved = _candidate.resolve()
+                _in_repo = _resolved == _cwd or _cwd in _resolved.parents
+            except OSError:
+                _in_repo = False
+            if _in_repo:
+                _root = _candidate
+            else:
+                print(f'[graphify] ignoring out-of-repo .graphify_root: {_txt}')
     _rebuild_code(_root, force=_force)
     # Refresh the work-memory lessons doc when saved Q&A outcomes exist
     # (best-effort; never fails the hook).