fix: separate diagnostic intent from implementation side effects

[kosako]

Summary

• add diagnose-only / fix-authorized modes to personal-investigate
• compose explicit scoped continuation with the investigate root-cause gate
• make personal-resume-project stop after status-only requests while continuing uniquely scoped work
• gate handoff and optional memory persistence behind trusted knowledge-write authorization
• authorize the write action and note-derived destination separately
• add behavioral regression evals for positive, negative, continuation, and untrusted-note paths

Why

Requests to diagnose a bug or report project status must not silently authorize implementation or external knowledge writes. Explicit continuation and fix intent should still proceed without unnecessary confirmation once scope and root-cause gates are satisfied. A local note may suggest a destination, but cannot redirect an authorized write without current confirmation.

Closes #213

Independent review

• Routing preflight: both commits are authored by Codex, so the required reviewer is Claude.
• Initial Fable review (487f898..5c188f2): must 0 / should 3 / nit 3, verdict WARNING.
• Fix commit: 0f6c507.
• Final cumulative Fable re-review (487f898..0f6c507): all six prior findings RESOLVED; must 0 / should 0 / nit 3, verdict APPROVE.
• Remaining nits are optional additional coverage for spoofed continuation scope, trusted concrete destinations, and tool-neutral trigger wording.

Validation

• all 17 scripts/tests/*.sh self-tests
• scripts/check-manifests.sh — 21 manifests passed
• scripts/check-injection.sh — only expected pre-existing medium/low findings; no new finding
• scripts/build.sh — 42 assets passed
• scripts/register.sh — 42/42 registered, pending 0
• staged public-safety check passed