docs(akroasis): correct Sphragis review boundary

[forkwright]

Summary

• follow up merged fix(akroasis): correct Pinax authority boundary #476 with the exact-head review corrections for its remaining Sphragis boundary drift
• state that Akroasis has no adopted Sphragis dependency; any preview use stays default-off and pins an immutable producer revision
• limit KAT evidence to conformance, keep hazmat prohibited, and assign qualified review/release promotion to forkwright/sphragis#43 while feat(reference-library): integrate Pinax persistence with Sphragis key epochs #395 owns the exact consumer handoff
• move the preview test command into an exact-revision Sphragis checkout or its matching CI context
• replace false “reviewed profile” claims with accurate versioned, unaudited, default-inert wording
• classify both maintained boundary documents as authored SSOTs instead of false frozen decision records

Tracker disposition

• References feat(reference-library): integrate Pinax persistence with Sphragis key epochs #395 without closing it.
• forkwright/sphragis#43 remains open and owns qualified cryptographic review and reviewed release promotion.
• design-input: hybrid PQ content-key wrapping (ECDH P-256 + ML-KEM-768) for multi-device vault #131 remains closed historical design context, not a live promotion owner.
• This PR neither implies nor records a favorable cryptographic review.

Verification

• cargo fmt --all -- --check
• git diff --check origin/main..HEAD
• Kanon deterministic lint and writing checks over the changed documentation
• no build, test, or full gate command was run, per operator direction

Base and collision check

• based on live main at 0a6cc2316fede4fff1a19662ebeda00c43743920, the merge commit for fix(akroasis): correct Pinax authority boundary #476
• release PR chore(main): release 0.6.2 #465 head 3a75328aeda6a8d0fe44af722068995953a0d8de changes only .release-please-manifest.json, CHANGELOG.md, Cargo.lock, and Cargo.toml; it does not overlap this four-doc patch