release: v0.5.15 — fix cache regression and structural cleanup

- cache.py: fix np.save extension bug from v0.5.13 — tmp path used
  final+".tmp" (abc.npy.tmp) but np.save auto-appends .npy to paths not
  ending in .npy, writing to abc.npy.tmp.npy instead; os.replace then
  raised FileNotFoundError silently, making every cache write a no-op
  and leaking *.npy.tmp.npy files. Fixed by inserting .tmp before .npy:
  tmp = final[:-4] + ".tmp.npy"

- config.py: remove str(default) round-trip in _getenv_int/_getenv_float
  — use raw = os.getenv(name); return default if raw is None else int(raw)
  so a future float default can't cause a spurious "not a valid integer"
  warning and return the wrong type

- executor.py: consolidate 4 progress.remove_task calls into one
  try/finally around the per-job body; continue inside try/finally
  executes the finally before the next iteration, making the invariant
  structurally enforced rather than relying on discipline across 4 sites

winnow/cache.py

@@ -83,7 +83,9 @@ class EmbeddingCache:
         """Store an embedding in the cache."""
         self._ensure_dir()
         final = self._path(asset_id, model)
-        tmp = final + ".tmp"
+        # Insert .tmp before .npy so np.save doesn't auto-append another .npy extension
+        # (np.save appends .npy to paths that don't already end in .npy).
+        tmp = final[:-4] + ".tmp.npy"
         try:
             np.save(tmp, embedding)
             os.replace(tmp, final)