feat(graph): cross-wing tunnels by shared topics (#1180)

When two wings have one or more confirmed TOPIC labels in common, the
miner now drops a symmetric tunnel between them at mine time so the
palace graph reflects shared themes (frameworks, vendors, recurring
concepts).

- llm_refine: TOPIC label routes to a dedicated `topics` bucket so the
  signal survives confirmation instead of getting collapsed into
  `uncertain` and dropped.
- entity_detector / project_scanner: bucket plumbed through the
  detection pipeline; `confirm_entities` returns confirmed topics
  alongside people/projects.
- miner.add_to_known_entities: optional `wing` parameter records the
  confirmed topics under `topics_by_wing` in
  `~/.mempalace/known_entities.json`. Wing names do NOT leak into the
  flat known-name set used by drawer-tagging.
- palace_graph: `compute_topic_tunnels` and `topic_tunnels_for_wing`
  create symmetric tunnels via the existing `create_tunnel` API so they
  share dedup and persistence with explicit tunnels.
- miner.mine: post-file-loop pass calls `topic_tunnels_for_wing` for
  the freshly-mined wing. Failures are logged but never abort the mine.
- config: `topic_tunnel_min_count` knob (env
  `MEMPALACE_TOPIC_TUNNEL_MIN_COUNT` or `~/.mempalace/config.json`),
  default 1.

Tests cover topic persistence through init->mine, tunnel creation when
wings share a topic, no tunnel below threshold, cross-wing tunnel
retrieval via `list_tunnels`, dedup on recompute, case-insensitive
overlap, and the end-to-end mine-time wiring.

Out of scope for this PR (called out in the PR body): manifest-
dependency overlap, per-topic allow/deny lists, search-result surfacing.

tests/test_miner.py

@@ -496,3 +496,104 @@ def test_add_drawer_stamps_normalize_version(tmp_path):
         assert meta["normalize_version"] == NORMALIZE_VERSION
     finally:
         del col, client
+
+
+def test_mine_creates_topic_tunnels_for_shared_topics(tmp_path, monkeypatch):
+    """End-to-end: when two wings have already-confirmed topics that overlap,
+    the miner's mine-time pass drops a cross-wing tunnel between them.
+
+    Issue #1180.
+    """
+    from mempalace import miner, palace_graph
+
+    # Redirect both the registry and tunnel-storage paths into tmp_path
+    # so we never touch the developer's real ~/.mempalace directory.
+    registry = tmp_path / "known_entities.json"
+    monkeypatch.setattr(miner, "_ENTITY_REGISTRY_PATH", str(registry))
+    miner._ENTITY_REGISTRY_CACHE.update({"mtime": None, "names": frozenset(), "raw": {}})
+    tunnels_file = tmp_path / "tunnels.json"
+    monkeypatch.setattr(palace_graph, "_TUNNEL_FILE", str(tunnels_file))
+
+    # Pre-populate the registry as if init had been run for two wings that
+    # share a topic.
+    miner.add_to_known_entities({"topics": ["foo", "bar"]}, wing="wing_one")
+    miner.add_to_known_entities({"topics": ["foo", "baz"]}, wing="wing_two")
+
+    # Mine wing_two — should drop tunnels between wing_two and wing_one
+    # for every shared topic. Just one in this case.
+    project_root = tmp_path / "wing_two_project"
+    project_root.mkdir()
+    write_file(
+        project_root / "notes.md",
+        "Some prose long enough to make a chunk. " * 20,
+    )
+    with open(project_root / "mempalace.yaml", "w") as f:
+        yaml.dump({"wing": "wing_two", "rooms": [{"name": "general"}]}, f)
+
+    palace_path = tmp_path / "palace"
+    mine(str(project_root), str(palace_path))
+
+    listed = palace_graph.list_tunnels()
+    assert len(listed) == 1
+    rooms = {listed[0]["source"]["room"], listed[0]["target"]["room"]}
+    assert rooms == {"foo"}
+    wings = {listed[0]["source"]["wing"], listed[0]["target"]["wing"]}
+    assert wings == {"wing_one", "wing_two"}
+
+
+def test_mine_no_tunnel_when_threshold_blocks_overlap(tmp_path, monkeypatch):
+    """Bumping ``MEMPALACE_TOPIC_TUNNEL_MIN_COUNT`` above the actual overlap
+    suppresses tunnel creation."""
+    from mempalace import miner, palace_graph
+
+    registry = tmp_path / "known_entities.json"
+    monkeypatch.setattr(miner, "_ENTITY_REGISTRY_PATH", str(registry))
+    miner._ENTITY_REGISTRY_CACHE.update({"mtime": None, "names": frozenset(), "raw": {}})
+    tunnels_file = tmp_path / "tunnels.json"
+    monkeypatch.setattr(palace_graph, "_TUNNEL_FILE", str(tunnels_file))
+    monkeypatch.setenv("MEMPALACE_TOPIC_TUNNEL_MIN_COUNT", "2")
+
+    miner.add_to_known_entities({"topics": ["foo"]}, wing="wing_one")
+    miner.add_to_known_entities({"topics": ["foo"]}, wing="wing_two")
+
+    project_root = tmp_path / "wing_two_project"
+    project_root.mkdir()
+    write_file(
+        project_root / "notes.md",
+        "Some prose long enough to make a chunk. " * 20,
+    )
+    with open(project_root / "mempalace.yaml", "w") as f:
+        yaml.dump({"wing": "wing_two", "rooms": [{"name": "general"}]}, f)
+
+    palace_path = tmp_path / "palace"
+    mine(str(project_root), str(palace_path))
+
+    # min_count=2 but only 1 shared topic → no tunnel.
+    assert palace_graph.list_tunnels() == []
+
+
+def test_mine_no_tunnel_when_only_one_wing_has_topics(tmp_path, monkeypatch):
+    """A wing in isolation (no other wing has confirmed topics) creates no tunnels."""
+    from mempalace import miner, palace_graph
+
+    registry = tmp_path / "known_entities.json"
+    monkeypatch.setattr(miner, "_ENTITY_REGISTRY_PATH", str(registry))
+    miner._ENTITY_REGISTRY_CACHE.update({"mtime": None, "names": frozenset(), "raw": {}})
+    tunnels_file = tmp_path / "tunnels.json"
+    monkeypatch.setattr(palace_graph, "_TUNNEL_FILE", str(tunnels_file))
+
+    miner.add_to_known_entities({"topics": ["foo"]}, wing="wing_one")
+
+    project_root = tmp_path / "wing_one_project"
+    project_root.mkdir()
+    write_file(
+        project_root / "notes.md",
+        "Some prose long enough to make a chunk. " * 20,
+    )
+    with open(project_root / "mempalace.yaml", "w") as f:
+        yaml.dump({"wing": "wing_one", "rooms": [{"name": "general"}]}, f)
+
+    palace_path = tmp_path / "palace"
+    mine(str(project_root), str(palace_path))
+
+    assert palace_graph.list_tunnels() == []