fix(db): ticket CLI always reads/writes main worktree database

Uses git rev-parse --git-common-dir to find the main worktree root,
then resolves the DB path there. Prevents WAL/journal pollution on
feature branch worktrees that caused merge conflicts on commonwealth.db.

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

db/connectors/ticket

@@ -24,6 +24,7 @@ All output is JSON on stdout.
 import json
 import os
 import sqlite3
+import subprocess
 import sys
 from pathlib import Path
 
@@ -31,10 +32,33 @@ SCRIPT_DIR = Path(__file__).resolve().parent
 CONFIG_PATH = SCRIPT_DIR / "config.json"
 
 
+def _main_worktree():
+    """Find the main worktree root via git's common dir.
+
+    In a worktree layout like:
+      settled-reach/main/       (main worktree, holds .git/)
+      settled-reach/server/     (linked worktree, .git is a file)
+    git rev-parse --git-common-dir always points to main's .git/,
+    so its parent is the main worktree root.
+    """
+    try:
+        common = subprocess.check_output(
+            ["git", "rev-parse", "--git-common-dir"],
+            stderr=subprocess.DEVNULL, text=True
+        ).strip()
+        return Path(common).resolve().parent
+    except (subprocess.CalledProcessError, OSError):
+        # Fallback: assume script lives in the main worktree
+        return SCRIPT_DIR.parent.parent
+
+
 def load_config():
     with open(CONFIG_PATH, "r") as f:
         cfg = json.load(f)
-    db_path = (SCRIPT_DIR / cfg["sqlite_db"]).resolve()
+    # Always resolve DB path in the main worktree to avoid
+    # WAL/journal pollution on feature branches causing merge conflicts.
+    main_root = _main_worktree()
+    db_path = (main_root / "db" / "commonwealth.db").resolve()
     cfg["sqlite_db_resolved"] = str(db_path)
     return cfg