fix: add _resolve_precon_dir() auto-detection so CFG.precon_dir is not empty

The precon deck list was missing after the monolith refactor because
PRECON_DIR was hardcoded in services/precon_service.py with no CLI arg,
env var, or auto-resolve fallback — unlike forge_jar, forge_dir, etc.

Changes:
- Add precon_dir field to Config class (models/state.py)
- Add --precon-dir CLI arg and PRECON_DIR env var support
- Add _resolve_precon_dir() with project-root, parent-dir, and
  forge_dir-relative detection; creates dir as fallback for downloads
- Refactor precon_service.py to use _get_precon_dir() helper that reads
  CFG.precon_dir at runtime instead of a hardcoded module-level Path
- Update routes/precon.py to use _get_precon_dir() for install endpoints
- Wire _on_startup to resolve precon_dir for uvicorn-direct launches
- Remove unused PRECON_DIR/PRECON_INDEX imports from routes/lab.py
- Audit confirms all other CFG path fields already have fallbacks

lab_api.py

@@ -64,6 +64,9 @@ app.include_router(ml_router)
 async def _on_startup():
     """Ensure DB and precon index are ready (supports uvicorn --reload)."""
     import routes.shared as _shared
+    # Ensure precon_dir is resolved even when started via uvicorn directly
+    if not CFG.precon_dir:
+        CFG.precon_dir = _resolve_precon_dir()
     _shared.init_collection_db()
     if not _shared.PRECON_INDEX:
         _shared.download_precon_database()
@@ -98,6 +101,7 @@ def _parse_args():
     p.add_argument("--forge-dir",   default=os.environ.get("FORGE_DIR", ""))
     p.add_argument("--forge-decks-dir", default=os.environ.get("FORGE_DECKS_DIR", ""))
     p.add_argument("--lab-jar",     default=os.environ.get("LAB_JAR", ""))
+    p.add_argument("--precon-dir",  default=os.environ.get("PRECON_DIR", ""))
     p.add_argument("--port",        type=int, default=int(os.environ.get("LAB_PORT", "8080")))
     p.add_argument("--ximilar-key", default=os.environ.get("XIMILAR_API_KEY", ""))
     p.add_argument("--pplx-key",    default=os.environ.get("PPLX_API_KEY", ""))
@@ -225,6 +229,33 @@ def _resolve_lab_jar() -> str:
     return ""
 
 
+def _resolve_precon_dir() -> str:
+    """Auto-detect the precon-decks directory.
+
+    The precon-decks dir lives in the project root and contains downloaded
+    .dck files plus precon-index.json.  We check relative to this file
+    (lab_api.py) first, then common sibling paths.
+    """
+    project_root = Path(__file__).parent
+    # 1. Standard location: <project-root>/precon-decks
+    candidate = project_root / "precon-decks"
+    if candidate.is_dir():
+        return str(candidate)
+    # 2. Check parent directory (in case running from a subdirectory)
+    candidate = project_root.parent / "precon-decks"
+    if candidate.is_dir():
+        return str(candidate)
+    # 3. Derive from forge_dir if available
+    if CFG.forge_dir:
+        candidate = Path(CFG.forge_dir) / "precon-decks"
+        if candidate.is_dir():
+            return str(candidate)
+    # 4. Fall back: create the directory in the project root so downloads work
+    fallback = project_root / "precon-decks"
+    fallback.mkdir(parents=True, exist_ok=True)
+    return str(fallback)
+
+
 def main():
     args = _parse_args()
     setup_logging(logging.DEBUG if args.verbose else logging.INFO)
@@ -233,6 +264,7 @@ def main():
     CFG.forge_dir       = args.forge_dir or _resolve_forge_dir()
     CFG.forge_decks_dir = args.forge_decks_dir or _resolve_forge_decks_dir()
     CFG.lab_jar         = args.lab_jar or _resolve_lab_jar()
+    CFG.precon_dir      = args.precon_dir or _resolve_precon_dir()
     CFG.port            = args.port
     CFG.ximilar_api_key = args.ximilar_key
     CFG.pplx_api_key    = args.pplx_key
@@ -245,6 +277,7 @@ def main():
     log.info(f"  Forge JAR:  {CFG.forge_jar or 'NOT SET'}")
     log.info(f"  Forge Dir:  {CFG.forge_dir or 'NOT SET'}")
     log.info(f"  Decks Dir:  {CFG.forge_decks_dir or 'NOT SET'}")
+    log.info(f"  Precon Dir: {CFG.precon_dir or 'NOT SET'}")
     log.info(f"  Lab JAR:    {CFG.lab_jar or 'NOT SET'}")
     log.info(f"  Results:    {CFG.results_dir}")
     log.info(f"  Ximilar:    {'configured' if CFG.ximilar_api_key else 'NOT SET'}")

models/state.py

@@ -20,6 +20,7 @@ class Config:
     forge_dir: str = ""
     forge_decks_dir: str = ""
     lab_jar: str = ""
+    precon_dir: str = ""
     results_dir: str = "results"
     port: int = 8080
     ximilar_api_key: str = ""

routes/lab.py

@@ -38,8 +38,6 @@ from routes.shared import (
     StartResponse,
     StatusResponse,
     AI_PROFILES,
-    PRECON_DIR,
-    PRECON_INDEX,
     build_java_command,
     run_batch_subprocess,
     _run_deepseek_batch_thread,

routes/precon.py

@@ -16,7 +16,8 @@ from pathlib import Path
 from fastapi import APIRouter, HTTPException
 
 import routes.shared as _shared                    # module reference, not value import
-from routes.shared import CFG, PRECON_DIR, download_precon_database, log
+from routes.shared import CFG, download_precon_database, log
+from services.precon_service import _get_precon_dir
 
 router = APIRouter(tags=["precon"])
 
@@ -36,7 +37,7 @@ async def install_precon(req: dict):
     if not file_name:
         raise HTTPException(400, "fileName is required")
 
-    src = PRECON_DIR / file_name
+    src = _get_precon_dir() / file_name
     if not src.exists():
         raise HTTPException(404, f"Precon not found: {file_name}")
 
@@ -71,7 +72,7 @@ async def install_precons_batch(req: dict):
 
     results = []
     for file_name in file_names:
-        src = PRECON_DIR / file_name
+        src = _get_precon_dir() / file_name
         if not src.exists():
             results.append({"fileName": file_name, "installed": False, "error": "not found"})
             continue

routes/shared.py

@@ -186,6 +186,7 @@ from services.import_service import (
 from services.precon_service import (
     PRECON_DIR, PRECON_INDEX, GITHUB_PRECON_URL, PRECON_CACHE_HOURS,
     load_precon_index, _sanitize_filename, _deck_to_dck, download_precon_database,
+    _get_precon_dir,
 )
 
 # ══════════════════════════════════════════════════════════════

services/precon_service.py

@@ -12,7 +12,9 @@ from urllib.request import urlopen, Request
 
 log = logging.getLogger("commander_ai_lab.api")
 
-PRECON_DIR = Path(__file__).parent.parent / "precon-decks"
+# Fallback default — used only when CFG.precon_dir has not been resolved yet.
+_DEFAULT_PRECON_DIR = Path(__file__).parent.parent / "precon-decks"
+
 PRECON_INDEX: list[dict] = []
 GITHUB_PRECON_URL = (
     "https://raw.githubusercontent.com/taw/magic-preconstructed-decks-data/"
@@ -21,9 +23,23 @@ GITHUB_PRECON_URL = (
 PRECON_CACHE_HOURS = 168
 
 
+def _get_precon_dir() -> Path:
+    """Return the active precon-decks directory from CFG, with fallback."""
+    from models.state import CFG
+    if CFG.precon_dir:
+        return Path(CFG.precon_dir)
+    return _DEFAULT_PRECON_DIR
+
+
+# Re-export for backwards compat — callers that import PRECON_DIR at module
+# level will get the default.  Runtime code should call _get_precon_dir().
+PRECON_DIR = _DEFAULT_PRECON_DIR
+
+
 def load_precon_index():
     global PRECON_INDEX
-    idx_path = PRECON_DIR / "precon-index.json"
+    precon_dir = _get_precon_dir()
+    idx_path = precon_dir / "precon-index.json"
     if idx_path.exists():
         with open(idx_path, "r", encoding="utf-8") as f:
             PRECON_INDEX = json.load(f)
@@ -61,7 +77,8 @@ def _deck_to_dck(deck_data: dict) -> str:
 
 def download_precon_database(force: bool = False) -> dict:
     global PRECON_INDEX
-    idx_path = PRECON_DIR / "precon-index.json"
+    precon_dir = _get_precon_dir()
+    idx_path = precon_dir / "precon-index.json"
     if not force and idx_path.exists():
         try:
             with open(idx_path, "r", encoding="utf-8") as f:
@@ -91,7 +108,7 @@ def download_precon_database(force: bool = False) -> dict:
         and (d.get('format') or '').lower() == 'commander'
     ]
     log.info(f"  Precons: Found {len(commander_decks)} Commander precon decks")
-    PRECON_DIR.mkdir(parents=True, exist_ok=True)
+    precon_dir.mkdir(parents=True, exist_ok=True)
     name_counts = Counter(_sanitize_filename(d['name']) for d in commander_decks)
     dup_names = {n for n, c in name_counts.items() if c > 1}
     index = []
@@ -102,7 +119,7 @@ def download_precon_database(force: bool = False) -> dict:
             sc = (deck.get('set_code') or 'unk').upper()
             safe_name = f"{safe_name}_{sc}"
         file_name = f"{safe_name}.dck"
-        dck_path = PRECON_DIR / file_name
+        dck_path = precon_dir / file_name
         commanders = deck.get('commander', [])
         cmdr_names = [c['name'] for c in commanders] if commanders else []
         total_cards = sum(c.get('count', 1) for c in deck.get('cards', [])) + sum(c.get('count', 1) for c in commanders)