fix(go): preserve generic receiver method ownership

[merlincat11]

Summary

Fixes #832.

Go methods declared on generic receiver types were emitted as top-level
functions because the receiver parser did not unwrap generic_type nodes.
The fix unwraps generic and pointer receiver nodes to their base type
identifier, preserving method ownership for both T[P] and *T[P] receivers.

Validation

• uv run --extra dev pytest -q — 2399 passed, 5 skipped, 2 xpassed
• uv run --extra dev ruff check code_review_graph/parser.py tests/test_multilang.py
• Validated against Terraform's internal/addrs/graph.go: all 11
  DirectedGraph[T] methods now have parent_name='DirectedGraph'.

Repository-wide Ruff still reports unrelated pre-existing violations in other
test files.

[github-actions]

code-review-graph review

Overall risk: 0.30 (LOW) — 4 changed function(s)/class(es), 0 affected flow(s), 2 test gap(s)

Risk-scored changes

Risk	Level	Symbol	Location	Tested
0.30	low	code_review_graph/parser.py::CodeParser	code_review_graph/parser.py:2403	yes
0.25	low	code_review_graph/parser.py::CodeParser._get_go_receiver_type	code_review_graph/parser.py:14696	no
0.05	low	tests/test_multilang.py::TestGoParsing	tests/test_multilang.py:12	no
0.05	low	tests/test_multilang.py::TestGoParsing.test_generic_methods_attached_to_receiver	tests/test_multilang.py:85	(test)

Test gaps

• code_review_graph/parser.py::CodeParser._get_go_receiver_type (code_review_graph/parser.py:14696)
• tests/test_multilang.py::TestGoParsing (tests/test_multilang.py:12)

Token savings: this graph-backed report used ~204,014 fewer tokens (~100%) than reading every changed file in full (estimated, chars/4 approximation).

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