fix: address codex round 2 — revert harvest break + allow lookback 0

- harvest.py: revert break to continue — mtime ordering can diverge
  from embedded ended_at timestamps (copy/touch), so we must check all
  files rather than early-exiting on the first old one
- cycle.py: use `is not None and > 0` so lookback_hours=0 means
  "scan full history" (opt-out of the cutoff)
- __main__.py: propagate --lookback-hours 0 to config as explicit 0

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

skillopt_sleep/__main__.py

@@ -111,8 +111,10 @@ def _cfg_from_args(args, task_meta: Dict[str, Any] | None = None) -> Any:
         overrides["codex_home"] = os.path.abspath(args.codex_home)
     if getattr(args, "source", ""):
         overrides["transcript_source"] = args.source
-    if getattr(args, "lookback_hours", 0):
+    if getattr(args, "lookback_hours", None) is not None and args.lookback_hours != 0:
         overrides["lookback_hours"] = args.lookback_hours
+    elif getattr(args, "lookback_hours", None) == 0:
+        overrides["lookback_hours"] = 0  # explicit opt-out: scan full history
     if getattr(args, "edit_budget", 0):
         overrides["edit_budget"] = args.edit_budget
     if getattr(args, "max_sessions", 0):