feat: deck dropdown, user-decks pipeline, deckgen fixes, gpt-oss removal

- Add user-decks/ directory and USER_DECKS_DIR config for exported decks
- Update export-to-sim to write to user-decks/ with static mount in lab_api
- Replace import/paste UI with API-backed "My Decks" dropdown in LAN client
  and AI Lab, fetching from GET /api/lab/decks with source grouping
- Fix GET /api/lab/decks to JOIN deck_cards for totalCards count
- Fix deckgenerator: add missing DOM elements (dg-strategy-bar, dg-stats-bar,
  dg-card-groups) inside #dg-results, null guards on render functions,
  fix setLoading always hiding results
- Replace gpt-oss:20b with claude-opus-4-20250514 across all files
- Add user-decks/ to _BUILTIN_DECK_DIRS in deck_service.py
- Enrich missing type_line from Forge card cache in DB deck path
- Collapse import bar behind <details> toggle in AI Lab

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

models/state.py

@@ -35,6 +35,7 @@ class Config:
     forge_jar: str = ""
     forge_dir: str = ""
     forge_decks_dir: str = ""
+    user_decks_dir: str = ""
     lab_jar: str = ""
     precon_dir: str = ""
     results_dir: str = "results"
@@ -57,6 +58,10 @@ CFG.lab_jar           = os.environ.get("LAB_JAR", "")
 # PRECON_DIR / PRECON_DECKS_DIR are aliases -- prefer PRECON_DIR
 CFG.precon_dir        = os.environ.get("PRECON_DIR") or os.environ.get("PRECON_DECKS_DIR", "")
 CFG.forge_decks_dir   = os.environ.get("FORGE_DECKS_DIR", "")
+CFG.user_decks_dir    = os.environ.get(
+    "USER_DECKS_DIR",
+    os.path.join(os.path.dirname(__file__), "..", "user-decks")
+)
 
 
 def validate_forge_config() -> None: