feat(lanes): let claude and codex lanes coexist at the same cwd

Repo/Adopt mode (POST /api/lanes/ensure) treated lanes.cwd as globally
unique, so adopting a path already driven by one CLI silently ignored a
different tool choice. Uniqueness moves to the composite (cwd, tool):
one directory can now back a claude lane and a codex lane side by side.

- server/db.js: drop the column-level UNIQUE on cwd, migrate existing
  DBs via table rebuild, add idx_lanes_cwd_tool.
- resolveLaneByCwd gains an optional tool filter; hook ingestion always
  pins to "claude" since Codex has no hook mechanism here, so a hook
  event never touches a codex lane sharing the path.
- POST /ensure resolves the existing owner by (cwd, tool) instead of
  cwd alone, so a different tool creates a sibling lane.
- LaneConsolePane's cwd-only lane lookups now also match tool, so a
  shared cwd doesn't attach a run to the wrong sibling lane.

Worktree mode is unaffected (already allocates a unique directory per
lane). docs/LANES.md and CLAUDE.md updated to describe the new
composite uniqueness.

server/db.js

@@ -414,7 +414,7 @@ db.exec(`
   CREATE TABLE IF NOT EXISTS lanes (
     id INTEGER PRIMARY KEY AUTOINCREMENT,
     title TEXT NOT NULL DEFAULT '',
-    cwd TEXT NOT NULL UNIQUE,
+    cwd TEXT NOT NULL,
     branch TEXT,
     pipeline TEXT NOT NULL DEFAULT 'default',
     session_id TEXT,
@@ -585,6 +585,74 @@ try {
   ).run();
 }
 
+// Migrate: cwd used to be single-column UNIQUE (one directory = one lane).
+// Codex and Claude Code lanes now coexist at the same adopted path, so
+// uniqueness moves to (cwd, tool) instead. SQLite can't ALTER TABLE to drop a
+// column-level UNIQUE, so rebuild the table when the old constraint is still
+// there — same rename-copy-drop pattern as the `agents` status rebuild above.
+// A fresh DB already gets the new column definition from CREATE TABLE.
+{
+  const laneTableInfo = db
+    .prepare("SELECT sql FROM sqlite_master WHERE type='table' AND name='lanes'")
+    .get();
+  if (
+    laneTableInfo &&
+    laneTableInfo.sql &&
+    laneTableInfo.sql.includes("cwd TEXT NOT NULL UNIQUE")
+  ) {
+    db.exec(`
+      PRAGMA foreign_keys = OFF;
+      BEGIN;
+      CREATE TABLE lanes_new (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        title TEXT NOT NULL DEFAULT '',
+        cwd TEXT NOT NULL,
+        branch TEXT,
+        pipeline TEXT NOT NULL DEFAULT 'default',
+        session_id TEXT,
+        run_id TEXT,
+        stage TEXT NOT NULL DEFAULT 'idle',
+        stage_since TEXT,
+        status TEXT NOT NULL DEFAULT 'idle',
+        gate_decision TEXT,
+        ci_status TEXT,
+        needs_action TEXT,
+        links TEXT NOT NULL DEFAULT '{}',
+        stages TEXT NOT NULL DEFAULT '{}',
+        notes TEXT,
+        created_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
+        updated_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
+        kind TEXT NOT NULL DEFAULT 'adopted',
+        source_repo TEXT,
+        base_branch TEXT,
+        slug TEXT,
+        tool TEXT NOT NULL DEFAULT 'claude',
+        detected_stage TEXT,
+        detected_signal TEXT,
+        detected_at TEXT,
+        slot INTEGER,
+        ports TEXT NOT NULL DEFAULT '{}',
+        active_feature_id INTEGER REFERENCES lane_features(id) ON DELETE SET NULL
+      );
+      INSERT INTO lanes_new SELECT
+        id, title, cwd, branch, pipeline, session_id, run_id, stage, stage_since,
+        status, gate_decision, ci_status, needs_action, links, stages, notes,
+        created_at, updated_at, kind, source_repo, base_branch, slug, tool,
+        detected_stage, detected_signal, detected_at, slot, ports, active_feature_id
+      FROM lanes;
+      DROP TABLE lanes;
+      ALTER TABLE lanes_new RENAME TO lanes;
+      COMMIT;
+      PRAGMA foreign_keys = ON;
+    `);
+    db.exec(`
+      CREATE INDEX IF NOT EXISTS idx_lanes_session ON lanes(session_id);
+      CREATE UNIQUE INDEX IF NOT EXISTS idx_lanes_slot ON lanes(slot) WHERE slot IS NOT NULL;
+    `);
+  }
+}
+db.prepare("CREATE UNIQUE INDEX IF NOT EXISTS idx_lanes_cwd_tool ON lanes(cwd, tool)").run();
+
 // Migrate: link agent rows to a workflow run. Workflow inner-agents are already
 // ingested as subagents (same subagents/ dir); these columns add the grouping +
 // phase that the run journal provides. Additive, safe on existing DBs.