fix(bundle): map primary keys for 7 unimportable node labels (#1322) - #1473

`CGCBundle._PK_MAP` had drifted behind the node tables declared in
`database_embedded_kuzu.py`. A label missing from the map falls through to the
`CREATE (n:Label) SET n = $props` branch of `_import_node_batch`, which Kùzu
rejects with "Create node n expects primary key name as input" — so an omission
is not a slow path, it is a hard failure for any bundle containing that label.

#1322 reports DbTable and ExternalClass. Diffing the map against the schema
found seven affected labels, not two:

  EnumMember, Mixin, Extension, Object   PK(uid)
  DbTable, Datasource, ExternalClass     PK(name)

The four uid-keyed labels also needed `_UID_PARTS` entries. Without them the
synthesised uid is the empty string, which would silently MERGE every node of
that label onto a single row — a data-loss bug rather than an error.

Still unfixed, deliberately: DbColumn PK(name, table_fqn) and RedisKeyPattern
PK(pattern, datasource_name). Composite keys need a multi-key MERGE and a wider
`_node_lookup_key` return shape than the current (label, field, value) tuple, so
they are out of scope here. `KNOWN_COMPOSITE_PK_LABELS` in the new test records
the gap explicitly instead of leaving it implicit.

Tests: `tests/unit/core/test_bundle_pk_map_coverage.py` derives expectations
from the schema file itself, so adding a node table without teaching the
importer about it now fails in CI instead of in a user's import. 8 of its cases
fail against the pre-fix code; all 26 pass after.

Closes #1322

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>