fix(security): restack scheduler descriptor drift detection

[seonghobae]

Purpose

Rebuild only the unique external-scheduler descriptor-stability delta from #372 directly on current protected main 2db716d7252603689b2cc18b700bac25e872b28f after #366 advanced the protected lineage. No predecessor check, review, scanner, or coverage evidence transfers.

The retained external scheduler evidence reader already opens a bounded regular file with O_NOFOLLOW and validates exact byte length. It now obtains descriptor metadata again after reading and fails closed if regular-file status, device, inode, size, modification time, or status-change time drifted while bytes were consumed.

Test-first lineage

• a0b03408fbbdb0184f4fba50f4871df5a612b64c — RED regression: post-read non-file/device/inode/size/mtime/ctime drift must be rejected and the descriptor must still close.
• 6b8c110655945b7301fa5d7337587fc12e727625 — GREEN implementation: second fstatSync binds accepted bytes to an unchanged descriptor snapshot.
• 637162d89a33a521d03c0d3c3869bb36f094c32a — current exact head; records POSIX.1-2024, Node filesystem, and NIST SSDF doctoring.

Current-base identity

Fresh compare against protected main is exactly three commits ahead, zero behind, with only:

• scripts/external-scheduler-evidence-audit.mjs
• test/external-scheduler-evidence-post-read-stability.test.ts
• docs/doctoring/external-scheduler-descriptor-stability.md

This is the clean current-main successor to stale #372. The old branch is not merge authority and its evidence is historical only.

Evidence boundary

This control detects bounded local descriptor mutation; it does not prove provider scheduler identity, enablement, production execution, host privilege isolation, release/deployment acceptance, or acquisition readiness. Higher-authority storage mutation and filesystem timestamp granularity remain explicit limits.

Do not merge until unchanged exact head 637162d89a33a521d03c0d3c3869bb36f094c32a has fresh terminal-success application ci, reviewer-ci, eligible protected-base central Security Scan, exact configured 100% owned-production statement/branch/function/line coverage, and zero valid unresolved findings. Pending, queued, skipped, absent, neutral, failed, cancelled, stale, predecessor, status-only, model-only, or rate-limited evidence is non-passing.

No force update, self-approval, gate weakening, reviewer/secret invention, repair/self-modifying workflow, outbound-license decision, release, deployment, or fabricated production evidence is introduced.

Related: #96. Supersedes #372.

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Review details

⚙️ Run configuration

Configuration used: Organization UI

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Run ID: 3d5e1419-d2d3-452f-8c97-a6c43f031569

📥 Commits

Reviewing files that changed from the base of the PR and between 2db716d and 637162d.

📒 Files selected for processing (3)

• docs/doctoring/external-scheduler-descriptor-stability.md
• scripts/external-scheduler-evidence-audit.mjs
• test/external-scheduler-evidence-post-read-stability.test.ts

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