fix: harden Claude compatibility and test gates

[CBEPX]

Summary

• harden Claude Code compatibility for Draft-07 review schemas, current model aliases including exact Opus 5, and Windows native/npm shim resolution
• make cancellation, process identity, lock recovery, stale-job reaping, and SessionEnd cleanup race-safe across POSIX and Windows
• expand isolated unit, integration, E2E, cross-platform, coverage, Node 18, and mutation gates
• release as v1.5.2; new contextWindow persistence telemetry remains a separate improvement while existing normalized telemetry stays compatible

Verification

• npm run check: 696 unit + 73 integration + 22 E2E, all passed
• npm run test:coverage: 91.42% statements/lines, 82.54% branches, 97.19% functions
• Node 18: 696 unit + 73 integration, all passed
• cross-platform suite: 413/413 passed; GitHub Windows, macOS, Ubuntu coverage, and Node 18 jobs all green
• mutation: forced claude-cli 66.03%, render 61.95%, state/tracked 73.69%; zero no-coverage/errors; PR mutation CI passed
• npm audit and npm audit --omit=dev: 0 vulnerabilities
• npm pack --dry-run: cc-plugin-codex-1.5.2.tgz, 76 entries, version/changelog gates passed
• Claude Opus 5 xhigh adversarial review: RELEASE APPROVE; targeted Windows preload follow-up also approved

Release boundary

• contextWindow persistence in every JSON payload is intentionally not added in this bugfix release because it expands telemetry and the public contract