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>

__tests__/fixtures/kernel-parity/torture.py

@@ -0,0 +1,49 @@
+"""Python torture fixture — decorators, self fn-refs, imports, shadowing."""
+import os, sys
+import os.path as osp
+from collections import OrderedDict, defaultdict
+from .relative import thing
+from mypkg.handlers import target_cb
+
+RETRY_LIMITS = {"a": 1}
+API_BASE = "https://example.test"
+x = compute(RETRY_LIMITS)
+
+
+class Service(BaseService, mixins.LoggerMixin):
+    """Class docs."""
+
+    def __init__(self, registry):
+        self.registry = registry
+        register(self.on_event)
+        queue(target_cb)
+
+    @staticmethod
+    def helper(arg):
+        return transform(arg)
+
+    async def run(self):
+        cfg = self.registry.lookup("x")
+        limit = RETRY_LIMITS
+        obj.method_chain().deep(cfg)
+        ", ".join(cfg)
+        return await fetch(API_BASE)
+
+    def on_event(self):
+        pass
+
+
+@app.route("/x")
+def view():
+    def inner():
+        return API_BASE
+    return inner()
+
+
+def shadowed():
+    API_BASE = "local"
+    return API_BASE
+
+
+handlers = {"recv": target_cb}
+callbacks = [target_cb, view]