caveman: disable on live host + SEC-017 + fail-closed compress guardrails ...

Council-reviewed follow-through on the caveman plugin (operator accepted the
recommendations). Three gated deliverables:

1. DISABLED on the live host: enabledPlugins."caveman@caveman"=false at user
   (~/.claude, uncommitted) + committed repo scope; env CAVEMAN_DEFAULT_MODE=off
   retained; marketplace kept for deliberate re-enable. Stops the per-turn
   third-party hook execution (which ran regardless of mode=off) at next
   session start.
2. SEC-017 opened (docs/security-ledger.md): supply-chain re-verify obligation
   pinning SHA 0d95a81 + self-remeasured baseline hashes; register = OPS (no
   D-number per GA-R3; precedent D-129). Open SEC 12->13, reconciled at Stage 4
   close (not an L10 trigger; CURRENT-STATE untouched).
3. Guardrails: repo-lint L11 FAILs on any *.original.md (caveman-compress
   residue), opt-out marker + harness T42-T44 (45/45 PASS); .claude/settings.json
   deny on Bash(*python3 -m scripts*)+Bash(*caveman-compress*); CLAUDE.md
   "Tooling guardrails" prohibiting the compressor against any repo-tracked
   prose. Rejected the proposed plugin-hash-baseline-in-repo-lint (layering
   violation; drift belongs in the SEC-017 re-verify duty).

Harness-config + governance only; no cloud mutation. repo-lint 0 fail;
gauntlet ALL GREEN (77). Changelog: docs/changelog-20260724-caveman-disable.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VUjEb7onHpdqFHUnio6iVw