fix(process): retain unrepresentable filename evidence

docs/process-capture.md

@@ -500,6 +500,11 @@ Every capture requires `truncation_details`, with separate accounting for:
   An unreadable directory is recorded in `enumeration_omissions` with its
   root-aliased path and operating-system error code. Entries observed before
   that directory remain available, while descendants beneath it stay unknown.
+  A basename that is not valid UTF-8 is never looked up through replacement
+  characters. It consumes entry capacity and records an `unrepresentable_name`
+  omission at its containing directory, with exact basename bytes in
+  `raw_name_hex` and a null `system_code`. That root's enumeration remains
+  incomplete, so missing paths beneath it remain unknown.
   Each retained regular file without a digest has an aliased path, size,
   remaining budget and reason: `file_bytes_budget`,
   `file_changed_or_short_read`, or `file_unavailable`. Its `system_code` is