fix(office-ui): stop progress-row flicker and surface native role replies end to end

Two user-visible defects in company mode, root-caused via project 6666/8888
DB forensics:

Progress-row flicker (thinking preview appearing/disappearing): progress
entries were broadcast to clients before reaching the persistence buffer,
so a tool_call-triggered session_detail snapshot rebuilt from the DB erased
freshly streamed entries from the live log. Buffer now fills before the
broadcast and session_detail flushes it before reading.

Native role transcripts incomplete (thinking only at start, no narration,
no final summary — external agents unaffected):
- thinking deltas shared one stream id per conversation turn while seq
  reset per iteration, collapsing all iterations into one entry and
  silently dropping live thinking from iteration 2 on; now keyed per
  iteration like assistant deltas
- assistant_delta events were mapped to None; company mode now surfaces
  them as streaming 'assistant' progress entries (rendered as Reply cards,
  merged like thinking, excluded from inline chat rows)
- thinking was persisted one row per token, flooding the 1000-entry cap
  and evicting interleaved tool history; append_progress now folds
  streaming deltas per (type, turn, stream) with seq dedup
- the terminal company turn was hidden at summary detail and, worse, its
  id-keyed backfill merge kept the first-inserted intermediate content, so
  the final reply never reached any channel; terminal turns are now
  flagged company_final_turn, visible at summary detail, and carry their
  own ui_message_id so they insert as fresh rows
- appendProgressEntry applied its seq guard against unrelated entries when
  the stream key was absent from the log, killing the first delta of any
  fresh stream; the guard now only applies within the same stream

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

opc/plugins/office_ui/snapshot_builder.py

@@ -230,6 +230,11 @@ def _transcript_message_hidden_from_ui(
 ) -> bool:
     metadata = dict(getattr(message, "metadata", {}) or {})
     kind = str(metadata.get("kind", "") or "").strip()
+    if metadata.get("company_final_turn"):
+        # The role's final reply of a company turn is the user-visible result
+        # (intake/aggregate turns have no engine-recorded result surface, so
+        # hiding this would drop the reply from the chat entirely).
+        return False
     return detail_level != "full" and kind in _FULL_DETAIL_ONLY_TRANSCRIPT_KINDS
 
 
@@ -1122,7 +1127,11 @@ def _transcript_item_to_ui_message(
             "role": role,
             "task_id": task_id,
             "transcript_kind": kind,
-            "detail_visibility": _transcript_message_visibility(kind),
+            "detail_visibility": (
+                "summary"
+                if message_metadata.get("company_final_turn")
+                else _transcript_message_visibility(kind)
+            ),
             **({"type": "system"} if kind == "runtime_v2_user_turn" else {}),
             **({"verification_verdict": verification_footer} if verification_footer else {}),
             **({"runtime_thinking": runtime_thinking} if runtime_thinking else {}),