FO product-edit guard loads write-core before mutation

[clkao]

FO write-scope classification now blocks direct product edits before mutation, keeping product changes on worker branches unless an exact captain override exists.

What changed

• Add host-neutral FO product-edit trace grading.
• Detect Codex and Claude file-write shapes before mutation.
• Require worker dispatch evidence for blocked product routes.
• Update FO shared-core and write-core guidance.

Evidence

• Focused contractlint/ensigncycle: 389/389 passed.
• Full and race suites: 2082/2082 passed each.

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