Docs: respect path boundary when clearing exclusions

add_directory cleared exclusions with a raw path.startswith(directory)
test, which also matched sibling directories sharing a name prefix —
adding /docs would silently un-exclude files under /docs2. Match the
directory itself or paths under it (directory + os.sep) instead.

src/personal_docs.py

@@ -246,8 +246,15 @@ class PersonalDocsManager:
         # Normalize the path
         directory = os.path.abspath(directory)
 
-        # Clear any exclusions for files in this directory
-        self.excluded_files = {p for p in self.excluded_files if not p.startswith(directory)}
+        # Clear any exclusions for files in this directory. Match on a path
+        # boundary (the directory itself or paths under it) rather than a raw
+        # string prefix: a bare ``startswith(directory)`` also matches sibling
+        # directories that merely share a name prefix (e.g. adding ``/docs``
+        # would wrongly un-exclude files under ``/docs2``).
+        self.excluded_files = {
+            p for p in self.excluded_files
+            if not (p == directory or p.startswith(directory + os.sep))
+        }
         self._save_excluded()
 
         if directory not in self.indexed_directories:

tests/test_personal_docs_exclusions.py

@@ -0,0 +1,51 @@
+"""Regression: add_directory must not un-exclude files in sibling directories.
+
+``add_directory`` clears exclusions for files inside the directory being added.
+It previously used a raw ``path.startswith(directory)`` test, which also matched
+sibling directories sharing a name prefix — so adding ``/docs`` would silently
+drop exclusions for files under ``/docs2``. The match must respect a path
+boundary.
+"""
+import os
+
+from src import personal_docs
+
+
+def _make_manager(tmp_path):
+    mgr = personal_docs.PersonalDocsManager(str(tmp_path))
+    # Pre-seed the directory as already tracked so add_directory takes the
+    # cheap "already indexed" branch (no indexing / refresh side effects); the
+    # exclusion-clearing logic under test runs unconditionally before that.
+    return mgr
+
+
+def test_sibling_directory_exclusions_survive(tmp_path):
+    docs = tmp_path / "docs"
+    docs2 = tmp_path / "docs2"
+    docs.mkdir()
+    docs2.mkdir()
+
+    sibling_excluded = os.path.abspath(str(docs2 / "secret.txt"))
+    mgr = _make_manager(tmp_path)
+    mgr.indexed_directories = [os.path.abspath(str(docs))]
+    mgr.excluded_files = {sibling_excluded}
+
+    mgr.add_directory(str(docs))
+
+    # The sibling-directory exclusion must remain — /docs2 is not under /docs.
+    assert sibling_excluded in mgr.excluded_files
+
+
+def test_own_directory_exclusions_are_cleared(tmp_path):
+    docs = tmp_path / "docs"
+    docs.mkdir()
+
+    own_excluded = os.path.abspath(str(docs / "old.txt"))
+    mgr = _make_manager(tmp_path)
+    mgr.indexed_directories = [os.path.abspath(str(docs))]
+    mgr.excluded_files = {own_excluded}
+
+    mgr.add_directory(str(docs))
+
+    # A file genuinely inside the added directory should be un-excluded.
+    assert own_excluded not in mgr.excluded_files