fix(contextual): narrow tool palette + forbid legacy read tools

Smoke trace 0b46841484ba7d024ed9f8d5ac8b1df0 showed the agent
defaulting to list_projects + get_project for a 'summarize
project Nexus' query, returning a shallow row without aiSummary
or tasks/notes. The legacy read tools were exposed via
*PROJECT_TOOLS / *TASK_TOOLS spreading.

Now _contextual_tools exposes exactly:
- get_page_details (sole read; supports per-entity + list views)
- create_task, update_task
- create_note
- create_timeline

Prompt rule 2 explicitly forbids the legacy reads, and the test
asserts they are excluded from the palette.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_run_contextual.py

@@ -74,3 +74,12 @@ async def test_run_contextual_stream_includes_scope_block(monkeypatch):
 
     # Note edit tools must NOT be exposed.
     assert "propose_note_edit" not in names, "propose_note_edit must be excluded"
+
+    # Legacy read tools must be excluded — they return shallow snapshots and
+    # cause the agent to under-answer (see trace 0b46841484ba7d024ed9f8d5ac8b1df0).
+    assert "list_projects" not in names, "list_projects must be excluded (legacy read)"
+    assert "get_project" not in names, "get_project must be excluded (legacy read)"
+    assert "list_tasks" not in names, "list_tasks must be excluded (legacy read)"
+    assert "get_task" not in names, "get_task must be excluded (legacy read)"
+    assert "list_notes" not in names, "list_notes must be excluded (legacy read)"
+    assert "get_note" not in names, "get_note must be excluded (legacy read)"