fix(telemetry): the human half of the pull ledger recorded one kind in three

Opening a snippet in the UI recorded rest_snippet. Opening a note or a task
recorded nothing — so the most direct evidence the product has that anyone
cares about a record existed for one kind out of three, and the other two sat
at zero pulls looking like dead weight beside a kind that merely had a counter.

Not an open question about intent: models/note_usage.py already documented
'rest_note' as a source value. Nothing wrote it. The design named it and the
implementation stopped at snippets.

Adds rest_note and rest_task. Tagged by SURFACE rather than by the record's
kind, matching rest_snippet — the kind is a join away, but which surface asked
is not recoverable after the fact. The mcp_/rest_ split stays load-bearing:
"is this dead weight" is served by any pull, "was that injected line useful" by
agent pulls alone, and a human clicking a link would inflate exactly the number
#1038 and #2085 gate on.

The vocabulary comment in the model was itself the stale-enumeration shape this
survey keeps finding — it named a source nothing wrote while omitting sources
that existed. Replaced with the naming CONVENTION plus a pointer to grep, which
cannot drift, rather than a longer list that would go stale the same way.

Guard extended to the REST surface, same derivation as the MCP half: a route
registered at exactly /<int:x> for GET is a detail view, and one reaching a
note-backed loader must record. Handler source is expanded one level through
module-private helpers, without which get_snippet_route — the route that
already got this right — would drop out of the check by loading via
_load_snippet. Verified the guard fires when a call is removed.

Renamed test_mcp_pull_telemetry.py -> test_pull_telemetry.py; it is no longer
only about MCP.

Closes #2476

src/scribe/models/note_usage.py

@@ -51,10 +51,23 @@ class NoteUsageEvent(Base):
     note_id: Mapped[int] = mapped_column(Integer, nullable=False)
     # 'surfaced' | 'pulled'
     event: Mapped[str] = mapped_column(Text, nullable=False)
-    # Which surface produced it: 'auto_inject' | 'write_path_place' |
-    # 'write_path_semantic' | 'mcp_get_snippet' | 'mcp_get_note' | 'rest_note'.
-    # Kept granular so the place arm and the semantic arm can be compared —
-    # that comparison is the whole reason the place arm needed logging at all.
+    # Which surface produced it. Kept granular so the place arm and the
+    # semantic arm can be compared — that comparison is the whole reason the
+    # place arm needed logging at all.
+    #
+    # A CONVENTION, not a fixed vocabulary: `mcp_<tool>` for an agent call,
+    # `rest_<kind>` for a human opening a detail view, and a bare name for a
+    # hook or background surface ('auto_inject', 'write_path_place',
+    # 'write_path_semantic'). This comment deliberately no longer lists the
+    # members — the previous list had gone stale, naming 'rest_note' that
+    # nothing wrote while omitting sources that existed, and a half-true
+    # enumeration reads as authoritative in exactly the way that misleads
+    # (#2476). `grep -rn record_pulled\\\|record_surfaced src/` is the
+    # authoritative list, and unlike a comment it cannot drift.
+    #
+    # The mcp_/rest_ split is load-bearing. "Is this dead weight?" is served by
+    # any pull; "was that injected line useful?" is served by AGENT pulls only,
+    # so never aggregate across the prefix without saying why (#1038, #2085).
     source: Mapped[str] = mapped_column(Text, nullable=False)
 
     __table_args__ = (