feat(kernel): R5 — Python and Go ports, gates passed, default-on

Python (codegraph-kernel/src/python.rs) and Go (src/go.rs) join the
native kernel, mirroring the wasm extractors bug-for-bug. Python:
decorated_definition docstrings/decorators (decorates refs only for
bare-identifier decorators — the call-kind quirk), function-in-class →
method, module-level assignments always extract as variable, from-import
per-name binding refs, self.x fn-ref candidates as bare names. Go:
receiver methods with Recv::name qualified names + contains edges to the
first earlier struct of that name, type_spec struct/interface
classification with embedding→extends and interface method nodes,
composite-literal instantiates keeping the package qualifier, top-level
var/const initializer walks attributed to the declared symbol (#693),
2-hop field chains (#1276), New().Method() re-encode (#645/#608), and
the GO_SPEC fn-ref layers.

Grammars: tree-sitter-python 0.23.6 + tree-sitter-go 0.23.4 crates, with
wasm vendored from the same tags (parser.c sha-matched) — both were
2023-era in tree-sitter-wasms.

Gates: extraction sweeps 100% (flask 83/83, django 3,035/3,038 +3
error-file deferrals, gin 99/99, prometheus 978/979 +1); full-init
dump-diffs byte-identical on flask (10,833 rows), gin (17,540), django
(360,794), and prometheus (213,758); torture fixtures enforced in npm
test. DEFAULT_ROUTED now covers typescript/tsx/javascript/jsx/java/
python/go. Full suite: 2,471 tests pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

codegraph-kernel/src/langs.rs

@@ -15,7 +15,8 @@ use tree_sitter::Language;
 
 /// Languages this kernel binary can extract (reported by contractInfo;
 /// TS-side routing policy decides what actually routes).
-pub const LANGUAGES: [&str; 5] = ["typescript", "tsx", "javascript", "jsx", "java"];
+pub const LANGUAGES: [&str; 7] =
+    ["typescript", "tsx", "javascript", "jsx", "java", "python", "go"];
 
 pub fn grammar_for(language: &str) -> Option<Language> {
     match language {
@@ -23,6 +24,8 @@ pub fn grammar_for(language: &str) -> Option<Language> {
         "tsx" => Some(tree_sitter_typescript::LANGUAGE_TSX.into()),
         "javascript" | "jsx" => Some(tree_sitter_javascript::LANGUAGE.into()),
         "java" => Some(tree_sitter_java::LANGUAGE.into()),
+        "python" => Some(tree_sitter_python::LANGUAGE.into()),
+        "go" => Some(tree_sitter_go::LANGUAGE.into()),
         _ => None,
     }
 }