feat(godot): parse .tscn scenes and .tres resources (L2/L4)

[sunerpy]

Summary

Second Godot static-analysis layer — parses scene and resource files into the graph (no engine, deterministic static parsing).

• .tscn scenes (L2): node tree, script = ExtResource(...) scene→script bindings, [connection signal from to method] signal-connection edges (→ handler method name), groups, and instance=ExtResource(...) instanced-subscene edges.
• .tres resources (L4): [ext_resource] id-table + script =/property ExtResource(...) → resource→script/resource reference edges, anchored on a lazily-emitted resource marker (zero output when a resource has no references).
• Shared godot_common.rs (res:// path mapping, quote/attr helpers) reused by all three parsers.

Scope discipline

• Reuses existing EdgeKind (References/Instantiates) and NodeKind::Constant — no new variants. Hand parser, no new dependency. Tolerant parsing (no panics on malformed). Handler-method/ExtResource targets are emitted as references by name; cross-file symbol resolution is the next layer (post_extract). Existing golden corpora byte-unchanged.

Verification

• make ci green; godot suites: scene 8/8, resource 7/7, project 8/8 (regression-safe). clippy -D warnings 0; guardrail 0; golden clean.
• Rebased on latest main (includes the daemon_idle de-flake).