Fix LadybugDB migration issues and JSON parsing

[HumanBean17]

Summary

Fix remaining issues from the KuzuDB → LadybugDB migration that were causing CI failures (exit code 139 segfaults) and test failures.

Root Causes Fixed

1. Segfault (exit code 139): tests/test_ladybug_queries.py still used kuzu.Connection and created .kuzu databases, which crashed when opened with LadybugDB code
2. JSON parsing failures: LadybugDB returns JSON without quotes around keys ({key: value}), but code used json.loads which expects standard JSON
3. Incomplete migration: Various references still used old kuzu naming (constants, error messages, CLI arguments)

Changes

Core fixes:

• Add _parse_ladybug_json helper to handle LadybugDB's non-standard JSON format
• Update meta() method to use helper for all JSON fields
• Fix _open_stale_ontology_graph to use ladybug.Connection and .lbug extension
• Fix fixture names (kuzu_db_path_cross_service_smoke → ladybug_db_path_cross_service_smoke)
• Fix helper functions in _builders.py (build_kuzu_to → build_ladybug_to)

Test updates:

• Add _parse_ladybug_json to test_ast_graph_build.py
• Fix constant references (KUZU_INCREMENTAL_TRACKING_ISSUE_URL → LADYBUG_INCREMENTAL_TRACKING_ISSUE_URL)
• Fix assertions for LadybugDB warning messages
• Fix attribute references (lbug_path → ladybug_path)

Documentation/CLI:

• Update error messages from "Kuzu graph" to "Ladybug graph"
• Update CLI argument --kuzu-path to --ladybug-path
• Update verbose logging message

Test Results

• All 741 tests pass
• Previously failing tests now pass:
  • test_ladybug_graph_refuses_ontology_version_below_required
  • test_find_route_callers_includes_producer_callers
  • test_find_route_callers_returns_route_caller_client_node
  • test_trace_request_flow_inbound_includes_caller_node_id
  • test_meta
  • test_graph_meta_present_and_versioned
  • test_ladybug_path_derived_as_index_dir_code_graph_kuzu
  • test_increment_emits_kuzu_stale_warning_block
  • test_increment_vectors_only_skips_graph

🤖 Generated with Claude Code

[HumanBean17]

Closing in favor of #303 — fixes pushed directly to that branch.