refactor: split precheck_core and migrate commands to commands/

- Split 900-line precheck_core.py into 9 focused modules:
  precheck_constants, time_utils, data_utils, state_manager,
  market_data, candidate_scoring, snapshot_builder,
  adaptive_profile, trigger_analyzer
- Remove dead auto_trader command and module
- Migrate 7 root-level command modules into commands/:
  check_api, doctor, external_gate, init_user_state,
  market_probe, paths, rotate_external_gate_log
- Keep thin backward-compatible facades in root package
- Update cli.py MODULE_MAP to route through commands/
- Verified compileall and smoke tests for all key commands

src/coinhunter/services/precheck_snapshot.py

@@ -2,8 +2,4 @@
 
 from __future__ import annotations
 
-from . import precheck_core
-
-
-def build_snapshot() -> dict:
-    return precheck_core.build_snapshot()
+from .snapshot_builder import build_snapshot