Merge scientific grounding and safety gate plan

[GreenSharpieSmell]

This PR adds the approved scientific grounding and safety gate plan and its signed change packet.

Summary:

• adds the scientific grounding and safety gate plan under validation/records/
• records 4/4 signoff in the corresponding change packet under validation/change_packets/
• resolves the Phase 0-A open-beam contradiction by making non-laser the default unless a Class 2 exception is explicitly approved
• requires OPERATOR_QUALIFICATIONS.md before benchtop work
• formalizes category boundaries between simulation, analogy, and physical validation

Status:

• Claude, Gemini, Rocks, and Codex have all approved the plan
• branch is synced with current main
• docs-only change; no tests were run

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Mark merged safety-gates record as accepted

This record is merged to main with 4/4 APPROVE signoffs in its change packet, but the header still says Status: proposed. Keeping the governing safety plan in a draft state can cause later readers or process checks to treat these gates as non-binding, which is risky for hardware-facing decisions this document is intended to constrain.

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