test(agent-context): cover symlink containment in the mtime fallback

The recursive fallback resolves each candidate before the relative_to()
containment check, but nothing exercised that path. Add a parity test for a
plan reachable only through a specs/ symlink pointing outside the project:
relative_to() is lexical and would accept it, emitting an in-project-looking
path for an out-of-project file. Both the bash twin and the Python port skip
it, so the "at <plan>" line is omitted.

Also correct the module docstring, which still described the fallback as
scanning specs/*/plan.md one level deep.

Author: Quratulain-bilal

extensions/agent-context/scripts/python/update_agent_context.py

@@ -11,8 +11,9 @@
 
 When ``plan_path`` is omitted, the script derives it from
 ``.specify/feature.json`` (written by /speckit-specify). Falls back to the most
-recently modified ``specs/*/plan.md`` only when feature.json is absent or its
-plan does not exist yet.
+recently modified ``plan.md`` found anywhere under ``specs/`` — scoped layouts
+nest it as ``specs/<scope>/<feature>/plan.md`` — only when feature.json is
+absent or its plan does not exist yet.
 """
 
 from __future__ import annotations

tests/extensions/test_update_agent_context_python_parity.py

@@ -343,6 +343,38 @@ def test_python_mtime_fallback_finds_nested_plan_matching_bash(
     assert b"at specs/backend/001-nested/plan.md" in content
 
 
+@requires_posix_bash
+def test_python_mtime_fallback_skips_plan_reached_through_escaping_symlink(
+    tmp_path: Path,
+) -> None:
+    """A plan reached via a specs/ symlink out of the project is not selected.
+
+    ``relative_to()`` is lexical, so ``specs/linked/001-x/plan.md`` looks
+    in-project even when ``specs/linked`` points outside the tree. Resolving
+    before the containment check rejects it, so the fallback finds nothing and
+    the ``at <plan>`` line is omitted rather than naming an out-of-project file
+    with an in-project-looking path. Mirrors the bash twin's ``_resolved_rel``.
+    """
+    repo_a, repo_b = twin_projects(tmp_path, context_file="AGENTS.md")
+    for repo in (repo_a, repo_b):
+        outside = repo.parent / f"outside-{repo.name}" / "001-x"
+        outside.mkdir(parents=True, exist_ok=True)
+        (outside / "plan.md").write_text("# plan\n", encoding="utf-8")
+        specs = repo / "specs"
+        specs.mkdir(parents=True, exist_ok=True)
+        (specs / "linked").symlink_to(outside.parent, target_is_directory=True)
+        # Sanity: the plan really is reachable through the symlink.
+        assert (specs / "linked" / "001-x" / "plan.md").is_file()
+
+    bash = run_bash(repo_a)
+    py = run_python(repo_b)
+
+    assert_parity(bash, py, repo_a, repo_b)
+    content = (repo_b / "AGENTS.md").read_bytes()
+    assert content == (repo_a / "AGENTS.md").read_bytes()
+    assert b"\nat " not in content
+
+
 @requires_posix_bash
 def test_python_prefers_feature_json_over_mtime_matching_bash(tmp_path: Path) -> None:
     repo_a, repo_b = twin_projects(tmp_path, context_file="AGENTS.md")