Tracking S3: atomic text publish primitive (A4) - safeWriteText

[easonLiangWorldedtech]

Tracking issue for the S3 / A4 PR (branch feat/atomic-publish-s3; PR to be opened after review).

Part of the file-write safety series — plan: easonLiangWorldedtech/Zoo-Code#33, epic: #1375. Item: S3 / A4 — Atomic text publish.

Scope

• New src/services/file-safety/safeWriteText.ts: atomic publish primitive — write to a staging temp file in the target directory, fsync, close, then atomic fs.rename over the target; optional backup flag (keeps a .bak copy of the previous contents, matching safeWriteJson semantics); win32 DACL preservation via icacls (rename fallback if it fails); platform injection for testability.
• src/utils/safeWriteJson.ts refactored to delegate to it (lock/merge/streaming behavior preserved; existing suite passes unchanged).
• DiffViewProvider.saveDirectly (the single funnel for all five write tools) switched from raw fs.writeFile to safeWriteText default options.

Acceptance

• No torn writes: readers observe either the old or the new full content (rename is atomic on both POSIX and NTFS)
• win32: file ACL preserved after publish (DACL copy); linux: covered via injected platform
• safeWriteJson suite green without changes (behavior preserved)
• CI green (ubuntu unit-test gate), 100% codecov patch coverage

Status

• PR: #1395 open, all CI checks green on head 1a2ade2a5 (ubuntu + windows unit, codecov/patch 100%, CodeRabbit review complete)
• CodeRabbit: 4/4 findings fixed, confirmed by the bot and replied (2026-08-27); 2 threads remain open only because the platform blocks bot self-resolve (same limitation seen on feat(task): per-task file observation registry (A2, #1375) #1394)
• Head: 1a2ade2a5 (amended after findings: mock-based cross-platform symlink test, DACL save-before/restore-after, fd try/finally, duplicate spec mock removed)
• Awaiting maintainer merge