Fixes BigscreenVR/spt-bs-releases#309

## Change

Preserves Hertz's gated regression commit `c0ef957189edea03842afc4fa3ee0ce2ab769544`, then adds remedy `eed9ff361bd094eb9bf7eee4d8acc71b2de8d74b` on main `39241675642648a21a3e5ceca0ca95bf6e988155`.

- Include `bringing_up` in SessionPoll's liveness-only census. The shared reconcile path now preserves the admitted endpoint's control/online state until its session is published. Published sessions remain distinct on the wire.
- Read the bring-up ledger before the published-session snapshot. Publication inserts the session before clearing the ledger; this snapshot order can observe both, rather than neither, across that transition. No overlapping locks.
- Add end-user changelog text, generated changelog, and requirement evidence tags. No deadline/retry changes, weaker assertions, healing/rebind, or #302 instrumentation.

The reorder rides on construction + Doyle's blind read, not a forced-transition rig. The three scheduled GREENs establish the held-prepublication-window remedy; they do not independently exercise publication between the two census reads.

## #309 proof — Windows, retries 0

Hertz's baseline scheduled RED/native100 and knob-unset GREEN/native0 are preserved in releases#309 comment 5692936213. No baseline RED was rerun or overwritten.

On the remedy product source:
- `bound_engine_room_survives_bringup_reconcile_and_receives_native_briefing`: three consecutive independent scheduled GREENs.
- Same cell with `SPT_TEST_ER309_KNOB_UNSET=1`: GREEN.
- All four: native0/driver0, `COMPLETE`, `CONFIRMED_GONE`, active_processes0. Separate immutable receipts and cleanup evidence for every attempt.
- All four used spt SHA-256 `8061afc1d5d53024c1736e969ec773a28afce13430fa5a074e3bc3a427fb2124`. These runs preceded the documentation-only additions and commit.
- Unchanged briefing-presented/attach/input-ACK/rc/livehost/redispatch/broker selection: 128/128 functional passes, with the LEAK qualification below. This was guarded nextest, not the four cells' native-containment launcher.
- `cargo clippy --workspace --locked`: exit0.
- `traceable-reqs 0.4.1 check --json`: exit0; 924/924 complete, zero findings.
- Generated docs check: exit0. Exact `Co-authored by: todlando` trailer verified from raw commit body.

## Unattributed suite-context LEAK — not blocking per Doyle REH66OWT

Cell: `livehost::tests::legacy_psyche_sweep_guard_is_id_specific_and_fail_safe`.

LEAK occurrence counts: **1/1 remedy-suite, 0/1 main-suite, 0/1 isolated each side, same pool/flags**. Both suite runs passed 128/128 with exactly equal selected-test inventories; each isolated run selected and passed exactly one test. Every invocation exited0 with retries0 and two test threads. Both isolated heads rebuilt before execution.

| Context | Source | Functional result | LEAK |
| --- | --- | --- | --- |
| Original remedy suite | remedy product source before commit | 128/128 | 1 |
| Main suite | `39241675642648a21a3e5ceca0ca95bf6e988155` | 128/128 | 0 |
| Isolated remedy | `eed9ff361bd094eb9bf7eee4d8acc71b2de8d74b` | 1/1 | 0 |
| Isolated main | `39241675642648a21a3e5ceca0ca95bf6e988155` | 1/1 | 0 |

Isolated test-binary SHA-256s: remedy `ea4a8b1d19320368333d6b0e9565be9c9f9c2a4f18957359a78614bf8dcfa01a`; main `f312d451e3a693e85154dd5c4d2b78dcfecc1c5b79b13ecefba47c6c0cd465b6`.

Attribution remains unresolved: these controls establish neither a pre-existing leak nor a regression introduced by this change. Post-run censuses observed no own-target processes; that does not explain the LEAK or establish native containment. Original output, exact inventories, binary hashes, and birth-pinned census rows are preserved. No further leak runs.

## Handoff

Restored `fix/309-bringup-liveness` at `eed9ff361bd094eb9bf7eee4d8acc71b2de8d74b`, rebuilt remedy binaries (exit0), and released the pool (native0/driver0; no own-target processes observed). Restored spt SHA-256: `b50a431e2103f412448c7255abb5612828f3994f58b3f00be53fa5cf9c4fef1e`; this is distinct from the earlier regression-run binary above.

Receipt index: `.spt/preserved/309/todlando-windows/handoff.json`. Phase directories: `scheduled-{1,2,3}`, `control-1`, `seams`, `checks`, `docs-check`, `leak-remedy`, `leak-main`, `seams-main`, `build-2`, `pool-release`.

Pool-release receipt SHA-256: `6191ae604d63d7750f6af7644cec04ba8c88501cce6c032d9456511aac862ba6`. Released warm target remains in `.worktrees/309-bringup-liveness/target`; final free space 140,477,853,696 bytes. The initial no-claim bootstrap refusal is retained; direct prebuilt xtask claim and subsequent build succeeded without override. No TAKEOVER-line claim.

Doyle owns gating and merge. #302 remains parked and is not part of this PR.