feat(log): log authority is the fleet default — adopt-at-open, oracle-gated; plus the power-cut throw-site cures and the loud torn-record contract

THE DEFAULT FLIP (ruled on proven evidence — at-ack survived 301/301
acked-writes-through-power-cut in block-layer fault injection; deferred
tree authority demonstrably loses flush-covered acks): a brain with NO
stored authority artifact now ADOPTS LOG AUTHORITY AT OPEN. The oracle
gates the flip exactly as the guarded adoption path always did — curable
divergences baseline-backfilled, the flip lands ONLY on a green verdict —
and a brain that cannot verify STAYS tree-authoritative loudly, with the
refusal recorded on the switch artifact so subsequent opens are cheap.
config logAuthority: 'defer' is the explicit documented opt-out (no
automatic adoption; declared flush-window loss; adoptLogAuthority() flips
later). A stored artifact always wins. RELEASES.md carries the posture.

Two standing .fails debt pins FLIP TO HOLDING under the default: the
at-ack crash-survival gap and the ack-at-log durability target — both now
permanent asserted truths, not aspirations.

POWER-CUT THROW SITES (fault-injection findings, brainy-alone config):
- A manifest-listed-but-unloadable column segment QUARANTINES at
  discovery (loud once, counted always, quarantinedSegments() exposed for
  the heal) and the field serves its remaining segments DEGRADED — never
  a raw throw killing every query on the field. Real storage faults still
  propagate untouched.
- Torn generation artifacts (NaN/garbage in manifest or counter) DISCARD
  with narration at the store's open and recovery re-derives — plus a
  defensive finite-integer guard at the init consumer. Never a RangeError
  killing an open.

THE LOUD TORN-RECORD CONTRACT: an existing-but-unparseable stored record
now surfaces as a typed, counted TornRecordError on every entity-read
surface (including fifteen previously-blind per-item batch catches);
ENOENT stays clean-absent; artifact readers with designed absent-recovery
keep null-tolerance behind the loud floor. Disk corruption can no longer
read as silent data invisibility.

Suite migration: the default's pins inverted deliberately, generation
baselines made relative, quarantine-contract pins rewritten to the ruled
behavior.

Gates: tsc 0 · unit 2065/2065 (159 files) · integration 826 (93 files) ·
conformance 31/31 · kill-matrix 15/15 · torn-open guards 2/2.

tests/integration/durability-kill-matrix.test.ts

@@ -109,14 +109,14 @@ describe('durability kill matrix — crash at every commit-path step, recover by
   /**
    * Flip a brain to durable-at-ack (log-authority) mode.
    *
-   * NOT via `adoptLogAuthority()`: the sanctioned flip REFUSES on a freshly
-   * materialized brain — its verification oracle reports the generation-0
-   * VFS-root baseline as a divergence (`state-differs` even after an
-   * identity-update backfill; verified 2026-08-10). This helper flips the
-   * SAME switch the sanctioned path flips (`setLogDurability('at-ack')`) and
-   * persists the SAME authority artifact, so a reopened brain also runs in
-   * log-authority mode. The durability semantics under test are governed
-   * entirely by that switch.
+   * NOT via `adoptLogAuthority()` (and the helper opens every brain with
+   * `logAuthority: 'defer'`, opting out of the 10.0.0 adopt-at-open fleet
+   * default): the sanctioned path runs the oracle and a baseline backfill,
+   * which appends its own generation — shifting the floor arithmetic every
+   * row pins. This helper flips the SAME switch the sanctioned path flips
+   * (`setLogDurability('at-ack')`) and persists the SAME authority artifact,
+   * so a reopened brain also runs in log-authority mode. The durability
+   * semantics under test are governed entirely by that switch.
    */
   async function flipToAtAck(brain: Brainy): Promise<void> {
     const storage = (