feat(graph): add proxies, generics, subgraph bridges, and binary imports

[tob-scott-a]

Summary

• add graph model support for node origins, proxy nodes, type parameters, edge attributes, and new graph edge kinds
• materialize unresolved calls as proxy nodes and add typed projections/subgraph connection APIs
• import external binary-analysis JSON graphs with binary nodes, call edges, external proxies, and source correspondences
• update parser generic extraction, README docs, CLI summary output, regression tests, and KAT fixtures

Verification

• uv run pytest -q tests/
• uv run ruff check src/ tests/
• uv run ruff format --check src/ tests/
• ty check
• Claude reviewed the final importer alias/source-mapping fixes and reported no blocking issues

Issues

• Does not directly close any currently open issue. Issue entrypoint_paths_to() misses TS class-method dispatch and over-reports for non-taint paths #30 is only indirectly mitigated by preserving unresolved calls as proxies; TS dispatch and taint precision remain open.