CK-QG1: enforce agent-kernel maintainability ratchet

[douglasmonsky]

Summary

• add the repository-private normalized replacement-kernel maintainability baseline
• enforce deterministic C/B/B findings against the exact baseline and origin/main without text exemptions
• preserve the frozen spike check and wire focused ratchet coverage into the existing validation seam

Validation

• focused checker, scope, schema, typing, and tests
• just vc: 1,347 functional tests and 13 invariant tests passed
• final sdist: 819,931 bytes (820,000-byte ceiling unchanged)
• final allowance_read_p95_ms: 598.615998, invariants_only (non-gating noise)
• staged GitNexus impact: LOW, no affected production process
• exactly one independent final reviewer; all three in-scope findings fixed

Authority

CK-QG1 only, exact accepted CK-08R0 base 306cef3. No sibling lane, public surface, projection, join, or later-packet work.

[douglasmonsky]

CK-QG1 bounded blocker: hosted package-isolation CI correctly rejected the PR merge commit after origin/main advanced from the mandated CK-08R0 base 306cef3 to CK-08R2 merge 53ab22c (#391). CK-08R2 introduced two above-threshold normalized findings: query/page_executor.py:PageExecutionRequest (score 23, count 1) and query/page_executor.py:PageExecutionRequest.post_init (score 22, count 1). Both Python 3.10 and 3.14 jobs failed at the maintainability gate.

The CK-QG1 baseline remains exact to CK-08R0 (SHA-256 c490d954a5e9d09c61f884d51e3b9d3196af5615887f409c36f8469d1b2b6cf9). I did not broaden the baseline, add an exemption, weaken C/B/B thresholds, or refactor sibling production code because those would violate the lane locks. PR and retained worktree are preserved pending orchestrator disposition.