fix: include class instantiations in callers

[bohe76]

Summary

• Include instantiates edges in caller traversal so class usages through construction/static class access are surfaced by getCallers, CLI callers, and MCP callers.
• Add a regression test that verifies a class instantiation is returned as a caller.

Validation

pm run build

px vitest run tests/graph.test.ts --minWorkers=1 --maxWorkers=1 --testTimeout=30000 --hookTimeout=30000 --no-file-parallelism

ode dist\bin\codegraph.js callers CodeGraph --path . --json now includes ryInitializeDefault and
etryInitIfNeeded class usage results.