feat(api): materialize protocol record structure

[LiranCohen]

Summary

• add explicitly bounded typed record materialization for query() and observe(), retaining each canonical Record beside its decoded value
• expose the minimal { record, value } materialized shape; add children only when direct singleton children are explicitly selected
• batch selected direct singleton children with one query per child path and wake observed views when those children change
• add local records.set() for protocol paths that declare $recordLimit.max: 1, with an authoritative grant-backed selection for delegated sessions
• support scalar or non-empty parentId selections through grouped $recordLimit projection, including an exact-parent LevelDB path that avoids protocol-wide scans
• keep singleton/path-selection type machinery internal and use straightforward collect, sort, and limit logic for selected parent groups

Closes #1460.

Test plan

• root lint and lint autofix
• affected package builds (dwn-sdk-js, api, browser)
• API type contracts and 113 focused API tests
• Level store and grouped record-limit tests (105 focused tests)
• full agent package suite (1,675 passed, 18 skipped)
• delegated Records.Read grant-required selection test
• grouped parent projection on Level, MySQL, PostgreSQL, and SQLite (previous PR-head CI)
• docs MDX/type generation (previous PR-head CI)

Notes

• materialization requires an explicit page limit and eagerly decodes that page; callers should retain raw Record handles and stream large payloads instead
• records.set() intentionally targets only the connected tenant local replica; remote targets and protocol-role invocation are outside this first operation

[LiranCohen]

CI triage for the failed agent shard on head 62e38d4a:

AgentDwnApi > processRequest() > handles RecordsSubscribe message accepted both writes but observed one of two asynchronous callbacks before the test immediately closed the subscription. PR #1464 only changes nested protocol-path subscription scope validation; this test uses a schema-only filter, so that branch is not reached.

The exact process/send RecordsSubscribe tests passed in five consecutive targeted local runs (10/10 cases). Treating this as a load-sensitive pre-existing test race and rerunning only the failed job; no production or test semantics changed to mask it.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
92.6% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud