Delegate session PCM prefill proof to the SDK runway helper

Depends on misofm/engine#797 and a published SDK containing its
waitForPcmRunway contract for final package acceptance. Independent of adapter
#95, #102 and app misofm/app#210; never hold their delivery for this work.

Smallest outcome and facts

Dense and sparse session opening/seek use the SDK's generic PCM runway proof,
leaving this adapter responsible for its producer and aggregate choreography.
Current source baseline is main
f833303f146de7cbe1705fe88ae68a6d6e0d4e45; refresh before implementation.
src/feed.ts, src/scratch.ts and src/stems/ring.ts already delegate to SDK
primitives. Only src/session.ts::waitForRunway duplicates the generic generation,
contiguity and ring-capacity proof. This is source-level ownership evidence.

Required change

1. Replace that algorithm with SDK waitForPcmRunway. Opening supplies existing
   source totals/rings, frame 0, generation 1 and the current two-second timeout;
   seek supplies its acknowledged target/full generation and the same deadline.
   Omit minimumFrames to retain today's full-capacity/EOF-clamped policy.
2. Keep source pump.seekFrames, feed attachment/prepareSeek, context-state
   checks, suspension/resumption, serialized transport, producer/refill work and
   terminal cleanup exactly at their current composition seam. The helper never
   grants permission to skip these steps or resumes audio itself.
3. Remove now-unused per-prefill observer construction and direct protocol
   checks. Keep the existing diagnostic/source-observation objects because they
   have independent callers. Do not alter ring/read cursor behavior or prefetch.
4. Translate PcmRunwayError into existing session.open/session.seek failures,
   preserving source ID, cause and timeout/mismatch distinction in details.
   Preserve abort/close semantics and meaningful SDK usage errors. No second
   fallback algorithm or copy retained after migration.
5. Preserve dense/sparse canonical BLAKE3/count checks, warm/cold worker limits,
   512 KiB reads, 128 KiB ingest bounds, 64 KiB zero checkpoints, source-specific
   cleanup/locks, current diagnostics and all playback behavior. No codec,
   storage framework, source-policy expansion or transport rewrite.

Focused proof and delivery

Files: src/session.ts, an existing error translation seam only if needed,
tests/session.test.ts, README and package/provenance pins when adopting the
published SDK. Reuse existing opening, suspended/running seek and failure tests:
full current-generation prefill before success, wrong generation/contiguity,
EOF, timeout/cancellation, close during seek, and restore-running only after
successful proof. Assert consumer preparation precedes the SDK call and a
failure still completes aggregate cleanup. SDK owns detailed ring unit cases;
do not duplicate its matrix or add an engine factory just for testing.

Root commits one focused-green implementation tranche. Run npm run check;
for a released candidate run existing packed-browser/publish-dry-run gates and
fresh-consumer dependency checks once. Package with another coherent adapter
release when available; do not delay #95/app plotting to manufacture batching.
Final published adoption needs exact SDK/adapter versions, merged source SHAs,
registry integrities and existing provenance/attestation checks. If it cannot
share #95's cut, use a stateless ordinary release issue for publication and
record that dependency explicitly; source availability is never registry proof.

Luna XHIGH implements; a fresh Astra MEDIUM independently verifies and fixes
concrete in-scope bugs only; coordinator is a separate fresh Astra MEDIUM.
Maximum five coherent attempts with one verdict each; preserve evidence and
rebrief after five failures. Root synchronizes numbered local/GitHub evidence,
integrates latest main, and closes after PASS, merged delivery, required CI and
the published adoption evidence; verify remote CLOSED. No new results claimed
by this scope-only brief.

Implementation checkpoint

Luna XHIGH replaces the duplicated observer loop with SDK waitForPcmRunway,
preserving aggregate opening/seek/feed/context/refill cleanup choreography and
translating PcmRunwayError with reason/source ID/original cause. README and the
existing mismatch assertion are updated. Build, types, format/source policy and
six focused session/runway tests PASS; logs /tmp/miso-796-audit/adapter101-*.
Only temporary accepted SDK 0.2.5 node_modules installation is used; no package,
lock or provenance pins change. Implementer reports two opening-race failures
reproducing without this patch under SDK 0.2.5; raw identification is being
collected and full integration acceptance must resolve them. Focused success
is not full-suite or registry acceptance. Root checkpoints this bounded source
tranche before independent Astra MEDIUM review and latest-main integration.

Independent attempt 1 source review

Fresh Astra MEDIUM independently reviewed source checkpoint 37697f2 (including
implementation 74b66c9) against the installed SDK 0.2.5 helper contract.
Source-scope verdict: PASS. No production-code correction was needed. Opening
passes source totals/rings, frame zero and generation one; seek passes the
acknowledged target/generation after awaiting producer seek and feed
prepareSeek. Both omit minimumFrames and retain the two-second timeout.
Context transitions, serialized transport, diagnostics and terminal cleanup
remain at their existing seams. Only PcmRunwayError is translated; its original
object is retained as cause, mismatch retains source ID, timeout retains its
separate reason, and other SDK/abort errors retain their cause chain.

The verifier strengthened existing mismatch/deadline tests to assert completed
pump/feed/host/context/lease cleanup and distinguish feed preparation timeout
from SDK runway timeout. Build, test compilation, lint and format checks PASS;
15 focused session tests PASS, including full-generation runway, tail/EOF,
prepare ordering, running restoration, cancellation and terminal cleanup.
Logs: /tmp/miso-796-audit/verify-adapter101-{build,test-compile,focused,lint,format}.log.

This is one attempt-1 source verdict, not final package acceptance. Full
npm run check, packed-browser, publish-dry-run and fresh-consumer gates remain
pending the combined #95 candidate and published dependency/provenance pins.
The two SDK console-map opening-race tests belong to #95's correction
9666188; they must be included in the final full suite. Metadata/lock still
name SDK 0.2.4 at this review checkpoint; no published-adoption claim is made.

Combined candidate acceptance — 2026-09-14

Fresh Astra MEDIUM independently accepts #101 in the combined adapter 0.5.7
candidate at verification checkpoint 3746df9: PASS. Registry SDK 0.2.5 is now
pinned exactly; fresh normal-installed tarball resolves one SDK with the archive
integrity recorded in #95. The full npm run check passes all 380 tests,
including the formerly failing single-console opening-map races. Corrected
packed-browser and publish-dry-run gates PASS, as do strict fresh-consumer types
and imports. No #101 production fix was needed; SDK runway errors retain their
cause/reason/source and aggregate opening/seek cleanup remains intact. Logs and
candidate archive identity are recorded in #95's independent candidate review.
This completes source/package candidate verification, not release completion:
merged required CI and actual adapter 0.5.7 publication/attestation and issue
synchronization remain required before claiming published adoption or closure.

Published delivery and final closure

Independent Astra MEDIUM final published-adoption verdict: PASS. PR #107 merged
as 09842280710425c8ab321b97d39ecb49b5fe75cc after required macOS Chromium/WebKit
qualification 34794520960
passed. The qualified PR and merged source have the same tree
ecbbecf4022bf5b7f559ad25b7ae5ce0cc3f59e0. OIDC publication
34794726491
completed successfully. Public adapter 0.5.7 depends exactly on registry SDK
0.2.5; concurrent adapter 0.5.6 had already been published, so its immutable
identity was preserved.

The independently downloaded public archive is byte-identical to the accepted
candidate: SHA-256 8a0b8ad2cc9f0973514c28b1b5d195a56485879835b5797299dc234a8e433c35,
SHA-1 eae2472b38da784fc488273588f176f579dc3c5e, integrity
sha512-XXAarTN8Wh2ENIujHTCKh07a+EXYgP4hVPsW2g2KoqNHliEzmOPAXadV3BWYf4L7zy/BM8vbiJDrGLw1BTAYzQ==.
A fresh normal registry installation passes public imports and strict types,
including the borrowed engine close exclusion, and resolves exactly one SDK
0.2.5 with its verified registry integrity. npm 11.19 cryptographically verified
package signatures/attestations; the independently checked SLSA v1 DSSE binds
the exact archive, repository, npm-publish workflow, main source commit above
and publication invocation 34794726491/attempts/1.

Durable independent report: /tmp/miso-796-audit/verify-adapter95-published-verdict.md;
registry archive: /tmp/miso-796-audit/misofm-engine-web-adapter-0.5.7-registry.tgz.
All source, package and published-adoption gates are PASS. Root synchronizes
this evidence upstream and the matching GitHub issue before verified closure.