fix(acl): make the visibility predicates pure builders; repair CI

Run 2888 failed with 7 tests down, both causes mine.

The real problem was a design flaw, not the tests: readable_notes_clause and
browsable_notes_clause each opened their own DB session to fetch the caller's
group ids. That made them unmockable at the call site, so every unrelated
service test suddenly had to know they existed and stub them — four modules
broke the moment a service started calling one, and one of my own stubs patched
the wrong name (readable_* where the code had moved to browsable_*).

Fixed at the root: group membership is now a SUBQUERY rather than a fetched
list, so both clauses are synchronous pure functions with no session. One fewer
round-trip per query, membership folded into the statement the caller was
already running, and nothing for callers' tests to mock. The "no groups means no
group arm" special case disappears too — an empty subquery simply matches
nothing.

Also: _fake_note in the process tool tests had no real user_id, so its
auto-MagicMock attribute reached session.get(User, ...) through the new
provenance check and SQLAlchemy rejected it. The fixture now takes a real
user_id defaulting to the bound caller, which makes "is this shared?"
meaningful, and gains a case asserting another user's process comes back
flagged.

Test assertions on compiled SQL are deliberately loose about formatting: the
local env has no SQLAlchemy (rule #10), so they check that the arms exist rather
than guessing at exact rendering.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RLwAaV4DQEmVyn496HnEvt

tests/test_mcp_tool_processes.py

@@ -13,11 +13,14 @@ def _bind_user():
     _user_id_ctx.reset(token)
 
 
-def _fake_note(id=1, title="Drift Audit", note_type="process"):
+def _fake_note(id=1, title="Drift Audit", note_type="process", user_id=7):
     n = MagicMock()
     n.id = id
     n.title = title
     n.note_type = note_type
+    # Must be a real int, not an auto-attribute: the provenance check compares it
+    # against the bound caller (7) to decide whether the record is shared.
+    n.user_id = user_id
     n.to_dict.return_value = {"id": id, "title": title, "note_type": note_type}
     return n
 
@@ -53,6 +56,26 @@ async def test_get_process_returns_body_and_candidates():
         out = await get_process("drift")
     assert out["id"] == 7
     assert out["other_matches"] == [{"id": 9, "title": "Drift Audit Notes"}]
+    # The caller's own process carries no provenance marker — absence of the flag
+    # is what makes it read as theirs.
+    assert "shared" not in out
+
+
+@pytest.mark.asyncio
+async def test_get_process_flags_another_users_process():
+    """A shared Process must arrive labelled. get_process's contract is 'follow
+    the returned body', so an unlabelled one would put someone else's procedure
+    in charge of the session."""
+    note = _fake_note(id=7, user_id=9)
+    with patch("scribe.services.notes.resolve_process",
+               AsyncMock(return_value=(note, []))), \
+         patch("scribe.services.access.describe_provenance",
+               AsyncMock(return_value={"shared": True, "owner": "alex",
+                                       "permission": "viewer"})):
+        from scribe.mcp.tools.processes import get_process
+        out = await get_process("deploy")
+    assert out["shared"] is True
+    assert out["owner"] == "alex"
 
 
 @pytest.mark.asyncio