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/helpers/durabilityKillMatrix.ts

@@ -60,15 +60,25 @@ export function makeTempDir(): string {
  * Open a writer brain over `dir` with every implicit durability knob off:
  * persistence policy 'manual' (the engine never flushes on its own, so every
  * durable transition in a test is an explicit `flush()`/commit), deterministic
- * embeddings (tests always pass explicit vectors anyway), silent logs.
+ * embeddings (tests always pass explicit vectors anyway), silent logs — and
+ * `logAuthority: 'defer'` (the explicit opt-out of the 10.0.0 adopt-at-open
+ * fleet default), so the durability POSTURE is explicit per row too: rows
+ * pinning deferred/tree recovery semantics get exactly that, and at-ack rows
+ * engage log authority via `flipToAtAck`. The fleet default's open-time
+ * adoption would inject a baseline-backfill generation into every floor
+ * computation and pre-flip every row.
  */
-export async function openBrain(dir: string): Promise<Brainy> {
+export async function openBrain(
+  dir: string,
+  opts?: { logAuthority?: 'adopt' | 'defer' }
+): Promise<Brainy> {
   process.env.BRAINY_DETERMINISTIC_EMBEDDINGS = 'true'
   const brain = new Brainy({
     requireSubtype: false,
     storage: { type: 'filesystem', path: dir },
     silent: true,
-    persistence: { policy: 'manual' }
+    persistence: { policy: 'manual' },
+    logAuthority: opts?.logAuthority ?? 'defer'
   })
   await brain.init()
   return brain