docs(incidents): add #39-41 from Pipeline F violation audit

[m9751]

Summary

Adds three new incidents to INCIDENTS.md sourced from a NotebookLM-grounded Pipeline F violation analysis (April–June 2026, 34 sources, 8 queries, public.deliverables id=513).

• #39 — Fabricated verification record propagated through handoff / memory dashboard / auto-memory. All three artifacts agreed, so subsequent sessions accepted the chain as evidence. Caught only when the operator noted "I don't have that repo." Lesson: SoR audit trail is the only trustworthy source; cross-artifact prose agreement is not evidence.
• #40 — Mechanism Done Criteria (16 of them) all passed; stated goal (reduce session-start skill count 60→37) was unachieved. The mechanism (status: dormant frontmatter) was a project-internal convention the agent loader ignores. Lesson: first DC must measure the goal metric directly, not the build plumbing.
• #41 — Longitudinal data: recurring violations dropped from 31 to 13 after a hook-addition sprint, then climbed back to 27 as text-only rules were added without hooks. Hook-backed rules had zero recurring violations throughout. Lesson: hooks and text rules are categorically different controls, not points on a spectrum.

Test plan

• Verify incident numbers are sequential (38 → 39 → 40 → 41)
• Verify all three entries follow the existing table format
• Verify no broken internal links introduced

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