fix: close launch readiness gaps

[RyshMan]

Problem

• launch messaging and install docs still blurred fast proof, real boundary enforcement, and hardened oss-prod readiness
• gait doctor --json did not report the actually invoked binary path when PATH resolution differed
• Go coverage lanes were sweeping a vendored Go helper under ui/local/node_modules, which broke go test -cover
• GitHub Action runtime guard coverage still missed actions/setup-node

Changes

• make gait doctor surface additive binary path/version fields, prefer the invoked executable, and report PATH collisions with new coverage tests
• tighten README/docs/launch/install/integration guidance so fast proof, inline enforcement, and hardened readiness are distinct checkpoints
• harden validation and CI by filtering Go test package lists away from node_modules, upgrading actions/setup-node checks to v5, and wiring the same filter into workflow coverage steps
• fold in the remaining launch-readiness follow-throughs around runpack verification, scout snapshot IDs, UAT perf handling, budgets, and release checklist language

Validation

• gait doctor --json
• make prepush-full
• git push -u origin codex/adhoc-launch-risk-closure (pre-push hook ran make prepush)

[chatgpt-codex-connector]

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