fix: repair quad CLI transport layer

[drvoss]

Summary

• resolve Windows CLI launchers with deterministic .exe > .cmd > .bat > .ps1 priority and explicit cmd/PowerShell shims
• send Claude, Codex, and Cursor prompts over stdin; send Agy prompts through native argv below the measured safety threshold or an isolated file reference otherwise
• add configurable per-tool and overall deadlines, transient-only retry, best-effort process-tree termination, and one sanitized diagnostic per tool
• replace brace slicing with strict direct/fenced/allowlisted-envelope parsing while accepting recorded unknown top-level keys and retaining strict finding validation
• add 17 actual-spawn transport regressions and correct the consensus-gate invocation contract

Measurement findings addressed

• M1: Agy -p requires a prompt argument; stdin never invoked the tool.
• M2–M5: Windows npm shims require launcher resolution and explicit cmd/PowerShell invocation; direct bare-name or full .cmd spawning can fail.
• M6: wrapper launches require best-effort process-tree termination.
• M7–M8: Agy argv has a Windows command-line ceiling, while large file-reference prompts work but need a longer timeout.
• M9–M10: Codex --output-schema and Agy --json-schema are intentionally not enabled because the measured schemas/output envelopes are incompatible.
• M11: the measured OAuth userinfo EOF is transient and succeeds on one retry; credential rejection remains non-retryable.
• M12: direct JSON or one measured envelope unwrap is sufficient; unsafe first/last-brace slicing is removed.

Verification

• npm test — 1,101 passed, 0 failed
• npm run validate — passed
• npm run lint:md — passed
• npm run check:plugins — passed, no drift
• npm run lint:skills — passed with the established 78 known failures and no drift
• npm run lint:plugins — 9/9 passed

Issue #9 status

This PR intentionally does not close issue #9. A live four-CLI smoke record must still be produced on the separate machine that has all four CLIs installed. This development machine has only Codex available, so the remaining live verification is outside this PR's evidence.