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/Cargo.lock

@@ -52,8 +52,10 @@ dependencies = [
  "regex",
  "sha2",
  "tree-sitter",
+ "tree-sitter-go",
  "tree-sitter-java",
  "tree-sitter-javascript",
+ "tree-sitter-python",
  "tree-sitter-typescript",
 ]
 
@@ -480,6 +482,16 @@ dependencies = [
  "tree-sitter-language",
 ]
 
+[[package]]
+name = "tree-sitter-go"
+version = "0.23.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b13d476345220dbe600147dd444165c5791bf85ef53e28acbedd46112ee18431"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
 [[package]]
 name = "tree-sitter-java"
 version = "0.23.5"
@@ -506,6 +518,16 @@ version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "009994f150cc0cd50ff54917d5bc8bffe8cad10ca10d81c34da2ec421ae61782"
 
+[[package]]
+name = "tree-sitter-python"
+version = "0.23.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d065aaa27f3aaceaf60c1f0e0ac09e1cb9eb8ed28e7bcdaa52129cffc7f4b04"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
 [[package]]
 name = "tree-sitter-typescript"
 version = "0.23.2"