Next lane #309, after W2b PR228 handoff — todlando.

Prerequisite: Hertz is building instrument-only test/309-er-briefing-regression from4b6b03cc in .worktrees/hertz-309-er-briefing. Await his gated commit + native RED/unset-control receipts; do not adopt bare4b6 or edit/build his tree. No own309 tree exists yet.

Acceptance/sequence:
1. Read delivered instrument contract/receipts and exact base tip, fetch it, preserve the regression commit in own .worktrees/<309-lane> branch. Own target/private home, ancestry+disk admission, pool claim and one-line producer announcement.
2. Establish red-first reconcile-arm regression at the real broker/bind/reconcile boundary; preserve the existing er_briefing_presented_e2e clause4 assertions and45s barrier. Do not re-run user-known failure merely to confirm it; use the delivered controlled instrument.
3. Define coherent broker-owned Live/Starting/Absent observation. KIND_SESSIONS currently snapshots published rows then bringing_up independently; publication/ledger clear between those reads must not create a false absence. Blindly unioning bringing_up into live misstates lifecycle and is insufficient.
4. Repair false-death mutations at spawn/reconcile authority boundary, including CONTROL_REAP_NO_SESSION/control cleanup and LIVENESS_RECONCILE_OFFLINE. Bound-before-HostedSession-publish remains eligible; WAKE_RESUME dedup is not a substitute for preserving online state.
5. Prove live bound endpoint remains eligible and briefing is taken via native-inject at the controlled pre-publication scheduling point. Capture per-predicate and terminal-normalize results. No longer briefing waits, retries or assertion weakening.
6. Tag matching doc/impl/unit/int evidence in same change; identify existing requirements before minting anything. Native focused gates + actual briefing consumer proof, traceable-reqs check. After behavioral proof strip probes, update docs/changelog/generated output, preserve provenance, release own pool and one PR with rig+fix to Doyle. No merge; Doyle gates.

Issue authoritative details: BigscreenVR/spt-bs-releases#309 and comment5666263268. Older RCA evidence .spt/preserved/hertz-attachment-NO4JJOEL/er-briefing-arm6-rca.json (SHA2563fc7ea651f626da5e5363a2d145ac8def8d57e0229355b0aa7b3417501de27ad). Do not promote its strong inference to measured fact before new instrument results.

After #309 only: #302 STEP1 meet-rotation discriminator stamps plus both-worker stacks; STEP2 conditional remedy per Doyle GUWNE6OC. Obtain/read the current contract before that lane; do not launch ahead of lane order.