feat(seance): אחזור-הקשר מריצות-קודמות של issue לצמצום blind-heartbeats (#220)

מוסיף get_predecessor_context(issue_id, limit) ב-paperclip_client — read-only,
מחזיר ריצות-heartbeat שהסתיימו על אותו issue (newest-first) עם ה-summary שכל
heartbeat משאיר ב-result_json, כך ש-wake טרי קורא מה קודמיו הסיקו במקום לגלות-מחדש
(ה-generic blind heartbeat). קשירת run→issue דרך wakeup_request_id→payload.issueId;
limit מוגבל 1..10.

- Port: pc_get_predecessor_context (read-only, לא עטוף-טלמטריה).
- endpoint: GET /api/operations/issues/{issue_id}/predecessor?limit=3.
- 3 בדיקות (fake-asyncpg: shaping+isoformat, clamp, empty). אומת חי read-only על
  issue בן 11 ריצות → מוחזרות מסקנות-דיספוזיציה אמיתיות.

Invariants: מקיים G12 (fetch מהמעטפת, המגע מהשער; אין REST/כלי-פלטפורמה בליבה),
G2 (מקור-predecessor יחיד). follow-up: MCP tool + HEARTBEAT (wake קורא בתחילת ריצה).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/paperclip_client.py

@@ -1132,6 +1132,54 @@ async def get_agent_health() -> dict:
     return {"ok": True, "items": items, "counts": counts}
 
 
+async def get_predecessor_context(issue_id: str, limit: int = 3) -> dict:
+    """Recent finished runs on an issue, newest-first, for session continuation (#220).
+
+    The "seance" idea from Gastown, grounded in our data: each ephemeral heartbeat
+    rediscovers context every wake (the generic *blind heartbeat*; see
+    [[project_comment_delivery_guarantee]]). This lets a fresh wake read what its
+    predecessors on the SAME issue concluded — the run ``summary`` each heartbeat
+    leaves in ``heartbeat_runs.result_json`` — instead of re-deriving from scratch.
+
+    Read-only. Runs are tied to the issue via ``wakeup_request_id`` →
+    ``agent_wakeup_requests.payload->>'issueId'`` (only finished runs are useful
+    as predecessors). ``limit`` is clamped to 1..10.
+    """
+    limit = max(1, min(int(limit), 10))
+    conn = await asyncpg.connect(PAPERCLIP_DB_URL)
+    try:
+        rows = await conn.fetch(
+            """SELECT h.id, h.status, h.started_at, h.finished_at,
+                      h.result_json->>'summary' AS summary,
+                      h.error_code, h.session_id_after, a.name AS agent_name
+                 FROM heartbeat_runs h
+                 JOIN agent_wakeup_requests w ON w.id = h.wakeup_request_id
+                 LEFT JOIN agents a ON a.id = h.agent_id
+                WHERE w.payload->>'issueId' = $1
+                  AND h.finished_at IS NOT NULL
+                ORDER BY h.started_at DESC
+                LIMIT $2""",
+            issue_id, limit,
+        )
+    finally:
+        await conn.close()
+
+    runs = [
+        {
+            "run_id": str(r["id"]),
+            "status": r["status"],
+            "started_at": r["started_at"].isoformat() if r["started_at"] else None,
+            "finished_at": r["finished_at"].isoformat() if r["finished_at"] else None,
+            "summary": r["summary"],
+            "error_code": r["error_code"],
+            "session_id": r["session_id_after"],
+            "agent_name": r["agent_name"],
+        }
+        for r in rows
+    ]
+    return {"ok": True, "issue_id": issue_id, "runs": runs}
+
+
 # Singleton project for the precedent-library extraction queue. One issue per
 # uploaded precedent — assigned to the CEO who runs the local-MCP extractor.
 _LIBRARY_PROJECT_NAME = "ספריית פסיקה — תור חילוץ"