T08-04-VERIFY-01 Capture disposable-publication live canary evidence

[edithatogo]

Parent track: #397nnOpen verification gate. Record a successful disposable-publication canary and compatibility-matrix receipt before T08-04 or P08 can close.

[edithatogo]

T08-04 live-verification preflight (2026-08-11):

• GitHub environment disposable-substack-canary exists with no reviewer gate, appropriate for the solo-maintainer policy.
• SUBSTACK_DISPOSABLE_PUBLICATION_URL and SUBSTACK_CANARY_PRODUCTION_URLS are configured.
• The deterministic lifecycle guard suite passes locally via npm run test:disposable-canary:unit.
• The live workflow remains undispatched (0 runs), intentionally avoiding a false or destructive receipt.
• Remaining owner-gated inputs: an authenticated disposable-publication cookie and a network-observed endpoint contract. Neither has been guessed or replaced with placeholder data.

This is readiness evidence only, not the required successful lifecycle receipt. T08-04 and this verification issue remain open until create/reconcile/revise/unschedule/cleanup all pass and cleanup is evidenced.