ck: continuity golden vectors + C/Rust decode agreement, cut 2 of #222 [host PASS]

[aien-dev]

Cut 2 of #222 (continuity C port). Host tests only: no QEMU, no kernel wiring, Store and disk code untouched. Contract status stays SPEC.

What changed

• crates/aienos-kernel/src/continuity_vectors.rs (test-only, cfg(test), no kernel behaviour change): emits D-1 golden vectors (22 vectors: AgentRoot both sources, manifests with 0/1/64 WAL ids + a seq-2 one, AgentState genesis/depth 1/depth 2, WAL status 1..6 x len 1/1024, a hostile fork-sum-overflow state, 5 branch ids) and D-2 verdicts (Rust verdict of every vector and every single-bit flip, class and reason text).
• Fixtures (plain text): native/kernel/tests/fixtures/continuity_vectors.txt, continuity_verdicts.txt. Regenerate: AIENOS_CONTINUITY_VECTORS_REGEN=1 cargo test -p aienos-kernel --lib continuity_vectors. Without the variable the Rust test fails if a fixture differs from freshly emitted bytes (checked by hand-tampering a fixture: FAILED as expected).
• test_continuity_codec.c: reads the fixtures at run time (argv[1] or Makefile CC_FIXTURE_DIR), reproduces every byte and ObjectId (cc_object_id and sv1_object_id), decode-then-encode identity, replays all 86598 D-2 verdicts, refuses tampered bytes / ObjectId / verdicts. Existing checks untouched.
• Fork-count sum: C already refused overflow (checked sum); added hostile vector and mutant MC-13 (unchecked sum). Rust ck: checked fork sum in Rust branch-table validation [host PASS] #232 and C agree.
• Mutants added to continuity-mutants: UNCHECKED_FORK_SUM, MANIFEST_LAST_WAL_ZERO (only the vectors see it), SKIP_D1, SKIP_D2 (test counts its comparisons, so skipping is a FAIL).
• Contract: status line, 1.5 (fork sum DECIDED), K-1 (cap implemented + tested, policy still PROPOSED because chunking needs an operator decision), 6.3 (D-1/D-2 DECIDED + IMPLEMENTED with evidence), section 7 (MC-13..16), section 9 (fork-sum row + D-2 result). P-1..P-3 left PROPOSED. GATES.md: rows 87h/87i HOST PASS for the C codec twin, new rows 87j/87k; gate stays NOT_RUN.
• Comments in continuity.rs/continuity_tests.rs that cited C line numbers now cite cc_state_validate (comment-only).

Findings

• D-2: 0 divergences over 86598 verdicts (accept/refuse, class and reason text).
• DEFERRED to the resolve cut: recovery challenges (both actions) and HMAC responses (TEST key 0x0f x32) are emitted as deferred lines but not checked; the C codec has no challenge/HMAC code.

Evidence (head 4783df7)

cargo test -p aienos-kernel --lib continuity:  test result: ok. 15 passed; 0 failed
make -C native/kernel test:  golden: 22 vectors, 86598 D-2 verdicts compared (C vs Rust)
                             test_continuity_codec: PASS (218 checks)
                             CK_CORE_HOST: PASS
make -C native/kernel sanitize: test_continuity_codec: PASS (218 checks); CK_CORE_HOST: PASS (sanitize)
make -C native/kernel continuity-mutants:
  mutant CC_MUTANT_SKIP_TAKE_BOUND: killed (26 checks failed)
  mutant CC_MUTANT_ACCEPT_RESERVED: killed (33 checks failed)
  mutant CC_MUTANT_CHILD_INDEX_LE: killed (5 checks failed)
  mutant CC_MUTANT_TRUNCATE_AT_CAP: killed (1 checks failed)
  mutant CC_MUTANT_UNCHECKED_FORK_SUM: killed (2 checks failed)
  mutant CC_MUTANT_MANIFEST_LAST_WAL_ZERO: killed (1 checks failed)
  mutant CC_MUTANT_SKIP_D1: killed (3 checks failed)
  mutant CC_MUTANT_SKIP_D2: killed (3 checks failed)
  mutant flag refused under CK_HARDWARE_STAGING
  CK_CONTINUITY_CODEC_MUTANTS: PASS

Logs: /tmp/cut2logs/ on the Spark (mut_final.log, cargo_final.log, maketest.log, san.log).

Co-authored with Claude. Not merged.

🤖 Generated with Claude Code

[aien-dev]

VERDICT: merge 4783df7
Evidence:

• No weakened tests: diff of existing Rust tests and C test removes only comment line refs; Makefile only adds mutants and fixture define; no asserts dropped.
• Mutants (log CONT-236-light-001535.log:110-117): all 8 killed by a real '^test_continuity_codec: FAIL' verdict (Makefile continuity-mutants rejects build failure/crash as FAIL); UNCHECKED_FORK_SUM and MANIFEST_LAST_WAL_ZERO alter codec behaviour in continuity_codec.c, SKIP_D1/D2 are count-checked.
• Docs match log: 22 vectors, 86598 verdicts, 218 checks (log:77-78); contract stays SPEC, NOT_RUN; GATES 87h-87k say HOST PASS, M4_CONTINUITY NOT_RUN.
• CI all green (skips are pre-existing), mergeStateStatus CLEAN. No .py, no .github edits.