fix(extract): exclude class refs from indirect_call edges (#2137)

[Rishet11]

Fixes #2137.

Problem

indirect_call detection treats any callable-def target identically, but classes are callable only via their constructor and are frequently referenced as descriptive values, not invoked. The guard therefore emitted false edges for:

• ORM args: select(KbArticle), db.get(KbArticle, id)
• Exception tuples: except (ErrorA, ErrorB) as exc:
• String-literal getattr resolving to a same-named class: getattr(run, "KbArticle", 0)

In the reported sample, ~287/689 (41%) of indirect_call edges targeted classes, inflating node centrality and creating misleading traversals.

Fix

One root cause covers all three symptoms: distinguish class defs from function defs.

• Add a callable_class_nids set parallel to the existing callable_def_nids.
• Mark class-def nodes with a _callable_class attribute (stripped before output, like _callable).
• Exclude class targets from indirect_call emission in both paths: intra-file _emit_indirect_by_name and the cross-file resolver guard.

Both class-node creation sites register into the new set, so coverage is language-agnostic:

• the generic config.class_types branch (Python/JS/TS/Java/C#/Swift/…)
• the Ruby Struct.new / Class.new / Data.define synthesis

Tradeoff (intentional)

Suppression is context-blind: a genuine higher-order class callback that is invoked per element (e.g. map(Point, coords), sorted(items, key=SomeClass)) also loses its indirect_call edge. This false-negative is far rarer than the false-positive noise removed and matches the issue's framing ("classes are passed as descriptors, not invoked"). Flagging it so this isn't mistaken for a zero-tradeoff fix.

Verification

• New regression test test_class_ref_is_not_indirect_call covers all three contexts (except-tuple, getattr, ORM arg) plus a real function callback that must still emit.
• Before/after on identical input (via git stash): 4 class-targeted indirect_call edges → 0, function callbacks preserved.
• tests/test_indirect_dispatch* + tests/test_extract.py: all pass; no regressions in the surrounding suites.

[Copilot]

Pull request overview

This PR reduces false-positive indirect_call edges by distinguishing class definitions from function/method definitions during extraction, and suppressing indirect_call edges that would otherwise target classes.

Changes:

• Track class-definition node IDs separately (callable_class_nids) and tag class nodes with _callable_class in the extractor engine.
• Suppress indirect_call emission when the resolved target is a class in both the intra-file resolver (_emit_indirect_by_name) and the cross-file resolver guard in extract.py.
• Add a regression test asserting class references in ORM args / exception tuples / getattr-literals do not become indirect_call targets, while a real function callback still does.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
tests/test_indirect_dispatch.py	Adds a regression test for suppressing class-target indirect_call edges while preserving real function-callback edges.
graphify/extractors/engine.py	Introduces callable_class_nids and marks class defs with _callable_class; suppresses intra-file indirect edges to classes.
graphify/extract.py	Excludes _callable_class targets from cross-file indirect_call emission and strips _callable_class before output.

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