chore: drop dead code, sync stale comments

- delete api/categorize.py: orphaned module, never imported. The live
  pzmm-types→category mapping is _types_to_category in mlos_sort.py.
- delete api/adapters.py:_autopick_ambiguous: 5-line wrapper around
  _apply_branch_rules with zero callers in current source.
- delete docs/backlog/polling-path-pz-build.md: described work that
  shipped — init/06_sort_jobs_pz_build.sql plus pz_build plumbing in
  jobs.create_job, app._route_to_job, and app._build_result_for_job.
- sync MAP_LINE convention comment in api/mlos_sort.py with the worker
  copy (Muldraugh, KY is appended at the end, not prepended at the
  front — see adapters.build_response:577).
- update init/04_required_wsids.sql header to reflect the authed-API
  fetch path (HTML scrape was retired in 3a34b71).
- soften the now-stale '~14 rows' count in app._strip_path_prefix's
  docstring.

api/app.py

@@ -131,10 +131,10 @@ class ResortRequest(BaseModel):
 def _strip_path_prefix(deps) -> List[str]:
     """Defensively normalize dep names. Strips leading backslashes (B42 path
     syntax: `\\StarlitLibrary` -> `StarlitLibrary`) and trims whitespace.
-    Worker._split_csv applies this at parse time, but ~14 mod_parsed rows
-    in the live DB were written before that fix landed and will only refresh
-    when their wsid's time_updated advances on Steam. Normalizing here keeps
-    missing-dep matching correct against legacy rows."""
+    Worker._split_csv applies this at parse time, but a handful of legacy
+    mod_parsed rows were written before that fix landed and will only
+    refresh when their wsid's time_updated advances on Steam. Normalizing
+    here keeps missing-dep matching correct against legacy rows."""
     out: List[str] = []
     for d in (deps or []):
         s = (d or "").strip().lstrip("\\")