test(p10-1d-followup): cpp snapshot exercises actual CppAstExtractor

Reviewer nit #3: the hand-built fixed_doc() only verified chunker 1:1
mapping. New tests invoke CppAstExtractor against tests/fixtures/sample.cpp
and snapshot the real extractor → chunker pipeline (14 blocks emitted
covering namespace::chunk::Class, ctor/dtor/operator/template/free-fn
convention, glue <top-level> blocks between units).

Adds kebab-parse-code as a dev-dep of kebab-chunk (same precedent as
kebab-parse-md). Both the existing hand-built test AND the new
extractor-driven tests are kept — the former for fast chunker-only
validation, the latter for end-to-end regression detection.

Added tests:
- code_cpp_ast_extractor_snapshot: asserts all 8 named symbol units are present
- code_cpp_ast_extractor_chunks_deterministic: chunker output is stable

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/kebab-chunk/Cargo.toml

@@ -16,12 +16,13 @@ tracing                    = { workspace = true }
 serde_yaml                 = { workspace = true }
 
 [dev-dependencies]
-# kb-parse-md / kb-normalize are dev-only — used by the snapshot integration
-# test to build a CanonicalDocument from a fixture Markdown file. Forbidden as
-# regular deps per design §8 (chunker consumes CanonicalDocument from kb-core
-# only); `cargo tree -p kb-chunk --depth 1` (default scope, excludes dev-deps)
-# confirms this.
-kebab-parse-md = { path = "../kebab-parse-md" }
-kebab-normalize = { path = "../kebab-normalize" }
-serde_json      = { workspace = true }
-time            = { workspace = true }
+# kb-parse-md / kb-normalize / kb-parse-code are dev-only — used by the
+# snapshot integration tests to build a CanonicalDocument from fixture files.
+# Forbidden as regular deps per design §8 (chunker consumes CanonicalDocument
+# from kb-core only); `cargo tree -p kb-chunk --depth 1` (default scope,
+# excludes dev-deps) confirms this.
+kebab-parse-md   = { path = "../kebab-parse-md" }
+kebab-parse-code = { path = "../kebab-parse-code" }
+kebab-normalize  = { path = "../kebab-normalize" }
+serde_json       = { workspace = true }
+time             = { workspace = true }