fix(retrieval): the place arm marks its repeats too, and three tests meet the new contract (#4101)

CI on 5c64ea0 surfaced a half-measure I had shipped and three tests pinning the
semantics it replaces.

**The half-measure.** Only the semantic arm was marking repeats; the write
path's PLACE arm still dropped a nearby snippet that was on the ledger. One
menu, two rules, decided by which arm happened to find a record — and the
marker would then read as a complete account of what the session has met while
covering half the lines. `seen` now means this call's own menu and nothing
else, so both reuse arms mark and neither withholds.

**test_session_dedup_excludes_ids_from_the_reuse_arms** asserted the drop and
the ledger going into the query. Both are the defect; it is renamed and asserts
the marker instead.

**test_a_pulled_snippet_already_seen_is_evidence_not_menu** asserted #7 was
evidence and NOT menu, with the limit widened by one to pay for the drop. The
premise was the hard exclusion; #7 is now both, and the widening is no longer
needed for it.

**test_a_record_this_arm_withheld_itself_is_not_a_near_miss** is the
interesting one. Its property still holds and its setup no longer reaches it:
a ledger repeat comes back from the search and is rendered, so nothing is
withheld and `best_available` describes the bar. The one post-search filter
left is a PULLED record this same call already listed by place — kept in the
query because `resembles` needs its score, dropped from the menu because it is
already on it — so the test is rebuilt on that, and a sibling test pins the
direction that changed, so nulling the score whenever the ledger matches
cannot pass both.

Also stubs `superseded_ids` and `owner_names_for` in the new test file, which
were reaching for Postgres in a unit job.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

src/scribe/services/plugin_context.py

@@ -1611,7 +1611,13 @@ async def build_write_path_hint(
     # stay eligible here, which is the whole point of the split. Either way
     # they join `seen`, so the reuse arms (where the directory query would
     # surface them again) never re-list a record the sync block owns.
-    seen: set[int] = set(excluded)
+    #
+    # `seen` IS THIS CALL'S OWN MENU, and nothing else (#4101). It used to start
+    # from `excluded` — the session ledger — which folded two different claims
+    # into one variable: "already listed a few lines above" and "shown at some
+    # earlier point in the session". Only the first is a reason to stay quiet.
+    # The ledger is now a marker instead, on both reuse arms.
+    seen: set[int] = set()
     synced: list[dict] = []
     for item in here:
         nid = int(item["id"])
@@ -1625,7 +1631,12 @@ async def build_write_path_hint(
         if nid in seen:
             continue
         seen.add(nid)
-        placed.append(("nearby", item))
+        # MARKED HERE TOO, not just on the semantic arm, because these are one
+        # menu. A hint where some repeats carry `seen` and others are silently
+        # dropped — decided by which arm happened to find them — is worse than
+        # either rule applied consistently: the marker would read as a complete
+        # account of what the session has met before, and it would not be one.
+        placed.append(("nearby · seen" if nid in excluded else "nearby", item))
 
     # The stamping feed's "actually pulled it" half (#2791). Read once, before
     # the semantic arm, because the arm's query doubles as the resemblance
@@ -1657,20 +1668,11 @@ async def build_write_path_hint(
         query = concept_query(query) or query
     if remaining > 0 and query:
         t0 = time.perf_counter()
-        # `seen` CARRIES TWO DIFFERENT CLAIMS, and only one of them is a reason
-        # to withhold (#4101). It was built as the ledger plus everything this
-        # call has already rendered, and the arm treated both the same way:
-        #
-        #   - already in THIS menu (the sync block, the place arm) — listing it
-        #     twice in one hint is noise with no reader it could help;
-        #   - on the LEDGER from an earlier call — a different claim entirely,
-        #     and the one #3750 says must be rendered rather than dropped.
-        #
-        # Splitting them is the whole change here. `in_menu` keeps its
-        # exclusion; the ledger becomes a marker on the line.
-        in_menu = seen - excluded
         # Pulled-and-already-listed ids stay in the query (as evidence for
         # `resembles`) but never in the menu, so the limit has to cover them.
+        # `seen` is this call's own menu now, which is the only thing left that
+        # is a reason to withhold (#4101).
+        in_menu = seen
         pulled_in_menu = in_menu & set(pulled)
         _rep_wp: dict = {}
         hits = await semantic_search_notes(
@@ -1948,11 +1950,11 @@ async def build_write_path_hint(
     for marker, item in menu:
         # A rendered repeat is not a new surfacing (#4101) — same cut the log
         # row takes, so this table and `retrieval_logs` keep agreeing about the
-        # same call (#3668). The place arm never reaches here with one: a nearby
-        # snippet on the ledger is skipped before it is ever placed.
+        # same call (#3668).
         if int(item["id"]) in excluded:
             continue
-        arm = "write_path_place" if marker == "nearby" else "write_path_semantic"
+        arm = ("write_path_place" if marker.startswith("nearby")
+               else "write_path_semantic")
         by_arm.setdefault(arm, []).append(int(item["id"]))
     for arm, ids in by_arm.items():
         record_surfaced(user_id=user_id, note_ids=ids, source=arm)