Bug: bundle import fails with "Create node n expects primary key name as input" - _PK_MAP missing DbTable/ExternalClass #1322

Bug Description

cgc bundle import fails with KuzuDB backend when the bundle contains DbTable or ExternalClass nodes:

Import failed: Failed to import bundle: Binder exception: Create node n expects primary key name as input.

Root Cause

cgc_bundle.py::_PK_MAP is missing entries for DbTable and ExternalClass, while database_kuzu.py correctly defines their primary keys as name.

database_kuzu.py schema (correct):

CREATE NODE TABLE DbTable (name STRING, ..., PRIMARY KEY (name))
CREATE NODE TABLE ExternalClass (name STRING, ..., PRIMARY KEY (name))

cgc_bundle.py::_PK_MAP (missing entries):

_PK_MAP = {
    'Repository': 'path', 'File': 'path', 'Directory': 'path',
    'Module': 'name',
    'Function': 'uid', 'Class': 'uid', 'Variable': 'uid',
    'Trait': 'uid', 'Interface': 'uid', 'Macro': 'uid',
    'Struct': 'uid', 'Enum': 'uid', 'Union': 'uid',
    'Annotation': 'uid', 'Record': 'uid', 'Property': 'uid',
    'Parameter': 'uid',
    # <- DbTable and ExternalClass are MISSING!
}

When _import_node_batch() encounters these nodes, pk_field resolves to None, falling into:

# Line 993-995 in cgc_bundle.py
else:
    query = f"CREATE (n:{label_str}) SET n = $props"
    result = session.run(query, props=properties)

This CREATE statement provides no primary key, which KuzuDB rejects.

Reproduction

1. Index a Java project with MySQL datasource configured (generates DbTable nodes)
2. Export bundle: cgc bundle export project.cgc --repo .
3. Import into fresh KuzuDB: cgc bundle import project.cgc
4. Error occurs when processing the first unlisted node type

Real-world bundle tested: gc-starter-2.3.0.5.RELEASE (Java Spring)

• Total: 14,842 nodes, 26,312 edges
• DbTable: 17 nodes / ExternalClass: 265 nodes
• Affected: 282 nodes + 613 edges

Fix

_PK_MAP = {
    # ... existing entries ...
    'DbTable': 'name',
    'ExternalClass': 'name',
}

Just add two lines to cgc_bundle.py:942.

Underlying Architectural Issue

cgc_bundle.py and database_kuzu.py maintain independent PK mapping copies. DRY violation - every new node type requires manual sync across two files. Likely to cause similar bugs for DbColumn, RedisKeyPattern, ExternalFunction, etc.

Environment

• cgc v0.5.1, Python 3.13, KuzuDB, Windows 11