docs(mcp): address Copilot review comments on cookbook recipe (#665)

Three nits flagged by Copilot review on PR #665:

- Line 185: typo "external- content" → "external-content".
- Line 212: the _variant_postprocess snippet referenced `parent_name`
  and `sku` locals that weren't bound in the shown excerpt. Restored
  the local declarations (`parent_name: str | None = None` and
  `sku = unwrap_unset(attrs_obj.sku, None)`) so the snippet is
  internally consistent.
- Line 306: dropped the team-specific "cowork retro" phrasing.
  Reframed as "originally a real supplier-item-code lookup that
  returned zero results from the legacy cache" — public, accurate,
  doesn't require context the reader can't reach.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dougborg

katana_mcp_server/docs/cookbook/catalog-search.md

@@ -182,7 +182,7 @@ END;
 
 Triggers fire for every write mode SQLite supports — ORM `session.add()`, Core
 `INSERT ... ON CONFLICT`, raw `exec_driver_sql`, even a future migration helper issuing
-`text(...)` SQL. That's the SQLite-recommended pattern for external- content FTS5 and is
+`text(...)` SQL. That's the SQLite-recommended pattern for external-content FTS5 and is
 what the typed cache uses now.
 
 The regression test that would have caught the original bug is
@@ -203,11 +203,15 @@ The relevant hook is `_variant_postprocess` in `typed_cache/sync.py`:
 ```python
 def _variant_postprocess(attrs_obj: Any, cache_row: CachedVariant) -> None:
     parent = unwrap_unset(attrs_obj.product_or_material, None)
+    parent_name: str | None = None
+    sku = unwrap_unset(attrs_obj.sku, None)
+
     if parent is not None:
         cache_row.parent_archived_at = unwrap_unset(
             getattr(parent, "archived_at", None), None
         )
-        cache_row.parent_name = unwrap_unset(getattr(parent, "name", None), None)
+        parent_name = unwrap_unset(getattr(parent, "name", None), None)
+        cache_row.parent_name = parent_name
 
     display_parts = [parent_name] if parent_name else [sku] if sku else []
     # ...append variant config_attributes...
@@ -302,8 +306,9 @@ Tokenize: `["00", "7018", "581", "003"]`. Match:
 column carries the space-joined supplier codes; all four tokens hit prefixes there.
 
 This is the [#473](https://github.com/dougborg/katana-openapi-client/issues/473) repro
-that lived in the cowork retro. It only works because the tokenizer splits on `\W+`;
-with the legacy `query.split()` the whole string was one unmatchable token.
+case (originally a real supplier-item-code lookup that returned zero results from the
+legacy cache). It only works because the tokenizer splits on `\W+`; with the legacy
+`query.split()` the whole string was one unmatchable token.
 
 ### Multi-token natural-language