fix(consistency): C-14 ghost-duplicate check + CLAUDE.md sync rule

Root cause analysis: calling create_workstream() before writing the workplan
file creates a ghost workstream with repo_id=null. When fix-consistency later
runs on the file, it creates a second workstream and writes its ID into the
file — leaving the ghost permanently active and showing false partial progress
in the dashboard.

C-14: after checking file-backed workstreams, query active workstreams on the
same topic with repo_id=null. Flag any whose title matches a file-backed
workstream as a probable ghost duplicate.

CLAUDE.md: add explicit "workplan ↔ DB sync rule" prohibiting create_workstream()
for file-backed work. Write file first, then make fix-consistency.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/consistency_check.py

@@ -18,6 +18,7 @@ Checks:
   C-11  task-unlinked            WARN  Yes  Task block has no state_hub_task_id
   C-12  orphan-db-task           WARN  No   DB task in workstream has no file backing
   C-13  workstream-auto-complete WARN  Yes  All DB tasks done but workstream still active
+  C-14  ghost-duplicate          WARN  No   Active topic workstream with no repo_id matches a file-backed title — probable ghost from premature create_workstream() call
 
 Usage:
     python scripts/consistency_check.py --repo SLUG [--fix] [--json] [--api-base URL]
@@ -581,6 +582,12 @@ def check_repo(api_base: str, repo_slug: str, repo_path_override: str | None = N
     # C-07 / C-08: orphan DB workstreams (have repo_id=this_repo but no backing file)
     _check_orphan_db(api_base, repo_id, set(file_ws_ids.keys()), report)
 
+    # C-14: ghost duplicate — active workstream on same topic with no repo_id whose
+    # title matches a file-backed workstream.  Root cause: create_workstream() called
+    # before the workplan file was written; fix-consistency then created a second
+    # workstream from the file, leaving the first as an invisible orphan.
+    _check_ghost_duplicates(api_base, workplan_infos, file_ws_ids, report)
+
     return report
 
 
@@ -619,6 +626,62 @@ def _check_orphan_db(
             )
 
 
+def _check_ghost_duplicates(
+    api_base: str,
+    workplan_infos: list[tuple],
+    file_ws_ids: dict[str, tuple],
+    report: ConsistencyReport,
+) -> None:
+    """C-14: detect active workstreams with repo_id=null whose title matches a
+    file-backed workstream — these are ghosts created by premature create_workstream()
+    calls before the workplan file existed.
+    """
+    # Build lookup: normalised title → file-backed workstream id
+    file_titles: dict[str, str] = {}
+    for _, meta, _ in workplan_infos:
+        ws_id = str(meta.get("state_hub_workstream_id", "")).strip().strip('"')
+        title = str(meta.get("title", "")).strip().lower()
+        if title and ws_id:
+            file_titles[title] = ws_id
+
+    if not file_titles:
+        return
+
+    # Gather topic_ids from all file-backed workstreams so we can query by topic
+    topic_ids: set[str] = set()
+    for ws_id in file_ws_ids:
+        ws = _api_get(api_base, f"/workstreams/{ws_id}")
+        if ws and ws.get("topic_id"):
+            topic_ids.add(ws["topic_id"])
+
+    for topic_id in topic_ids:
+        topic_ws = _api_get(api_base, "/workstreams", {"topic_id": topic_id, "status": "active"})
+        if not isinstance(topic_ws, list):
+            continue
+        for ws in topic_ws:
+            ws_id = ws["id"]
+            if ws_id in file_ws_ids:
+                continue  # legitimately linked
+            if ws.get("repo_id"):
+                continue  # C-07 covers repo-scoped orphans
+            ws_title = ws.get("title", "").strip().lower()
+            if ws_title in file_titles:
+                file_backed_id = file_titles[ws_title]
+                report.add(
+                    severity="WARN",
+                    check_id="C-14",
+                    message=(
+                        f"Ghost duplicate: active workstream '{ws.get('slug')}' "
+                        f"(id={ws_id[:8]}…, repo_id=null) has same title as "
+                        f"file-backed workstream {file_backed_id[:8]}… — "
+                        f"likely created via create_workstream() before workplan file existed; "
+                        f"archive it"
+                    ),
+                    db_id=ws_id,
+                    fixable=False,
+                )
+
+
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 # Fix engine
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