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

src/scribe/services/knowledge.py

@@ -94,7 +94,7 @@ async def query_knowledge(
 
     # No query = browsing. Narrower scope: a record shared directly with the
     # caller is search-only and must not appear in an ambient list.
-    visible = await browsable_notes_clause(user_id)
+    visible = browsable_notes_clause(user_id)
     async with async_session() as session:
         base = select(Note).where(visible)
 
@@ -152,7 +152,7 @@ async def _semantic_knowledge_search(
     try:
         # A typed query is an explicit act, so it reaches the caller's full read
         # scope — including records shared directly with them.
-        visible = await readable_notes_clause(user_id)
+        visible = readable_notes_clause(user_id)
         async with async_session() as session:
             pattern = f"%{q}%"
             base = (
@@ -231,7 +231,7 @@ async def get_knowledge_tags(user_id: int, note_type: str | None = None) -> list
     Follows the browse list rather than the read scope: a facet is itself a
     passive surface, and offering a tag that only a search-only record carries
     would filter the visible list down to nothing."""
-    visible = await browsable_notes_clause(user_id)
+    visible = browsable_notes_clause(user_id)
     async with async_session() as session:
         base = (
             select(func.unnest(Note.tags).label("tag"))
@@ -247,7 +247,7 @@ async def get_knowledge_counts(user_id: int, tags: list[str] | None = None) -> d
     """Per-type counts for the sidebar, over what this user can BROWSE — so the
     numbers match the list they sit beside rather than promising rows that only a
     search would surface."""
-    visible = await browsable_notes_clause(user_id)
+    visible = browsable_notes_clause(user_id)
     async with async_session() as session:
         # Count non-task types
         stmt = (
@@ -316,7 +316,7 @@ async def query_knowledge_ids(
         return [item["id"] for item in items], total
 
     # Browsing (see query_knowledge) — narrower scope.
-    visible = await browsable_notes_clause(user_id)
+    visible = browsable_notes_clause(user_id)
     async with async_session() as session:
         base = select(Note.id).where(visible)
 
@@ -347,7 +347,7 @@ async def get_knowledge_by_ids(user_id: int, ids: list[int]) -> list[dict]:
         return []
     # Fetching specific ids is explicit, so this takes the full read scope — the
     # ids came from either a browse or a search, and both must resolve.
-    visible = await readable_notes_clause(user_id)
+    visible = readable_notes_clause(user_id)
     async with async_session() as session:
         stmt = (
             select(Note)