feat(extract): Route+HANDLES for Django REST Framework @action methods

[DeusData]

Distilled from #647 (thanks @muskiteer for the DRF ViewSet extractor).

What

Django REST Framework ViewSets expose extra endpoints through @action-decorated methods:

class CustomerTaskViewSet(ViewSet):
    @action(detail=True, methods=["post"], url_path="approve")
    def approve_draft_with_charge(self, request, pk=None): ...

On main these methods carried no route_path, so Phase 2a created no Route node and no HANDLES edge for them — the endpoint was invisible in the graph (#603).

Fix

try_drf_action_decorator (internal/cbm/extract_defs.c): when a method's decorator identifier is action, read the methods / url_path / detail kwargs and set *out_path/*out_method. The existing decorator-route pipeline (ensure_one_decorator_route, Phase 2a) then creates the Route + handler→Route HANDLES edge in the established direction. Fallbacks: method name for url_path, "GET" for methods; detail=True → /{pk}/<seg>, else /<seg>.

Reproduce-first

handles_drf_action_python (edge_types_probe suite): a DRF @action method must produce ≥1 HANDLES edge. RED (0 edges) on main without the extractor, GREEN with it. Full suite green.

Scope note (why a distillation, not a merge of #647)

#647 bundled this extractor with an unrelated project-wide reversal of the HANDLES edge direction (handler→Route → Route→handler) across every framework. That reversal was (a) unnecessary — the test counts HANDLES direction-agnostically and the extractor alone closes #603 — and (b) a latent regression: pass_cross_repo.c's find_route_handler resolves a route's handler with WHERE e.target_id = <route> AND e.type='HANDLES' (assumes handler→Route) and was not updated, so cross-repo route→handler resolution would silently return 0. This PR keeps only the extractor and preserves the documented convention.

Known limitation

Multi-method actions (methods=["get","post"]) capture only the first method → a single Route. Left as a follow-up.

Closes #603

Co-authored with @muskiteer.