Apply audit fixes for pack-sequence (14 findings, 28 new tests)

Cross-validation audit by Codex + Opus identified 14 issues:

CRITICAL:
- Fix _find_subdir_ci() prefix match accepting wrong folders (e.g.
  Publish_old). Now uses exact case-insensitive match.

HIGH:
- Add pack-sequence CLI subcommand with unambiguous arg parsing.
  Deprecate --sequence on pack (nargs='+' consumed the target).
- Fix Windows UNC/drive path normalization in bpathlib.make_absolute()
- Fix ZIP failure losing traceback + progress bar stuck on error
- Fix os.path.commonpath crash on cross-drive paths (new
  derive_common_project helper)
- Fix progress bar saturating at 40% during trace (log scale)

MEDIUM:
- Add per-shot error isolation in sequence scan (collect all errors)
- Add memory warning for >50 files in sequence pack
- Improve pack-info.txt with dedup stats
- Wrap single Path in list for old operators (type consistency)

LOW/INFO:
- Document VERSION_RE pattern
- Add TASK_CHOICE_ITEMS empty guard

28 new tests in tests/test_sequence_pack.py, 0 regressions.

Co-Authored-By: Mario Hawat <mario@autourdeminuit.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

blender_asset_tracer/pack/__init__.py

@@ -245,6 +245,13 @@ class Packer:
         in the execute() function.
         """
 
+        if len(self.blendfiles) > 50:
+            log.info(
+                "Packing %d blend files. Peak memory may be high (~%.1f GB estimated).",
+                len(self.blendfiles),
+                len(self.blendfiles) * 0.005,
+            )
+
         self._progress_cb.pack_start()
         self._new_location_paths = set()
         self._output_paths = []
@@ -656,12 +663,22 @@ class Packer:
         with infopath.open("wt", encoding="utf8") as infofile:
             print("This is a Blender Asset Tracer pack.", file=infofile)
             if len(self._output_paths) > 1:
-                print("This pack contains the following blend files:", file=infofile)
+                print(
+                    "This pack contains %d blend files:" % len(self._output_paths),
+                    file=infofile,
+                )
                 for op in self._output_paths:
                     print(
                         "    %s" % op.relative_to(self._target_path).as_posix(),
                         file=infofile,
                     )
+                print(
+                    "Total unique assets: %d" % len(self._actions), file=infofile
+                )
+                if self.missing_files:
+                    print(
+                        "Missing files: %d" % len(self.missing_files), file=infofile
+                    )
             else:
                 print("Start by opening the following blend file:", file=infofile)
                 print(

blender_asset_tracer/pack/zipped.py

@@ -83,7 +83,7 @@ class ZipTransferrer(transfer.FileTransferer):
                 except Exception:
                     # We have to catch exceptions in a broad way, as this is running in
                     # a separate thread, and exceptions won't otherwise be seen.
-                    log.exception("Error transferring %s to %s", src, dst)
+                    log.exception("Error writing %s to ZIP archive at %s", src, dst)
                     # Put the files to copy back into the queue, and abort. This allows
                     # the main thread to inspect the queue and see which files were not
                     # copied. The one we just failed (due to this exception) should also