fix(graph): surface instantiates edges in callers/callees (#774)

[maxmilian]

Fixes #774.

The actual gap (reframed)

#774 asks for class instantiation (Foo()) to count as a caller edge into the class. The extraction/resolution half already ships: resolveReferences() promotes a calls ref to an instantiates edge when the target resolves to a class (src/resolution/index.ts, covered by the existing test "promotes calls→instantiates when target resolves to a class (Python)"). And impact already surfaces it — getImpactRecursive walks every incoming edge except contains.

The residual bug is in traversal: getCallersRecursive and getCalleesRecursive whitelisted only ['calls', 'references', 'imports'], omitting instantiates. So after promotion, the edge exists in the graph but:

• callers <Class> / codegraph_callers returns "No callers found" even though the class is instantiated, and
• callees <site> omits the class the site constructs.

callers was the one inconsistent traversal (impact already included instantiation sites).

The fix

Add 'instantiates' to the edge-kind whitelist in both getCallersRecursive (incoming) and getCalleesRecursive (outgoing), so an instantiation site is reported as a caller of the class and the class as a callee of the site — matching what impact already does.

// getCallersRecursive
getIncomingEdges(nodeId, ['calls', 'references', 'imports', 'instantiates'])
// getCalleesRecursive
getOutgoingEdges(nodeId, ['calls', 'references', 'imports', 'instantiates'])

Test

Extends the existing calls→instantiates Python fixture (UserService + bootstrap) in __tests__/resolution.test.ts to assert the traversal: getCallers(UserService) now returns bootstrap via an instantiates edge, and getCallees(bootstrap) returns UserService. Red before the change, green after.

Validation

• npm run build — clean.
• The new regression test: red on main, green on this branch.
• npm test — no new failures. Two pre-existing worker-exit flakes (in resolution.test.ts's real-SQLite/wasm run) reproduce identically on clean main, so they're unrelated to this change; all callers/callees/impact suites (foundation, explore-blast-radius, object-literal-methods) pass.

The reporter's original evidence was against v0.9.5 (before the calls→instantiates promotion landed in #134), so the symptom they saw was broader; on current main this traversal whitelist is the remaining piece.

[maxmilian]

Closing — this was superseded upstream by d0e6499 (PR #804, also for #774), which adds the instantiates edge to getCallersRecursive/getCalleesRecursive in src/graph/traversal.ts — equivalent to this PR. Thanks for landing it!