feat(agent): add exact active System Record receiver

[Jurij89]

Summary

• Add the first default-off Stack D receiver kernel for one already-admitted ordinary active Agent Profile inventory row.
• Verify the exact signed authority closure, graph-scoped publication bundle, inventory-row binding, and owned-subject table before handing one immutable candidate to the lifecycle-owned materializer bridge.
• Extract the current head from the verified closure result instead of callback side effects, while retaining the first-artifact row-binding rejection that avoids unnecessary closure fetches.
• Bind canonical projection bytes and parsed quads into one verified-bundle value, reject any callback result whose bytes differ from the exact supplied bundle projection, and expose the verified envelope as an active-head type at the materializer boundary.
• Keep protocol registration, inventory traversal, admission, retries, reconciliation, tombstone/quarantine handling, lifecycle flags, timers, queues, and activation out of this PR; current node behavior remains unchanged.
• Avoid adding sync pressure: dependencies are captured once, row/artifact bytes are bounded before copying, unbound metadata is refused after the first head lookup, and no second copy of the complete closure is retained.

Related

• Continues Reconnect-triggered background sync amplification can starve foreground catch-up #2052; does not close it.
• First Stack D slice after merged producer/provider PR feat(agent): add default-off profile record producer and provider #2150.
• Targets integration/2052-system-record-sync and remains default-unused.
• Later Stack D PRs own bounded traversal/admission, tombstone/quarantine reconciliation, legacy gating, lifecycle/config wiring, and loaded regression evidence.

Diagrams

Active profile verification and apply kernel

Before:

sequenceDiagram
    participant Coordinator
    participant Receiver
    participant Repository
    participant Materializer
    Note over Coordinator,Materializer: No exact active-profile receiver kernel exists
    Coordinator-->>Receiver: No callable bounded verification/apply path

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After:

sequenceDiagram
    participant Coordinator
    participant Receiver
    participant Repository
    participant Materializer
    Coordinator->>Receiver: Already-admitted ordinary active row
    Receiver->>Repository: Resolve bounded content-addressed closure
    Repository-->>Receiver: Exact verified closure objects
    Receiver->>Receiver: Bind row, head, projection bytes/quads, and subject table
    Receiver->>Materializer: Immutable verified candidate plus separate signal
    Materializer-->>Receiver: Typed atomic-apply outcome
    Receiver-->>Coordinator: Preserve committed outcome after point of no return

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The receiver is not registered or called by production lifecycle code in this PR.

Files changed

File	What
packages/agent/src/system-records/receiver-v1.ts	Default-off active-row kernel, verified-closure extraction, coherent projection contract, exact row/table bindings, and lifecycle dependency snapshotting.
packages/agent/test/system-record-receiver-v1.test.ts	Active success, exact verifier inputs, multi-subject handoff, independent fail-closed row/table/projection/authority cases, cancellation point-of-no-return behavior, dependency snapshotting, and zero-fetch refusal coverage.

Test plan

• Build Core and Storage.
• Build Agent, including type tests and package-root verification.
• Run test/system-record-receiver-v1.test.ts (14/14).
• Run receiver, producer publication/validation, and provider suites together (65/65).
• Verify corrupted but valid subject-table bytes and mismatched projection bytes fail before consumeCandidate.
• Run git diff --check.
• Confirm the branch contains only receiver implementation/tests and no ignored or local-only files.

[Jurij89]

@otReviewAgent Please review the current head for merge readiness. This is the first default-unused Stack D receiver kernel; it does not register or activate sync, and its local resource/fail-closed gates plus live managed-ownership CI are green.

[Jurij89]

@otReviewAgent Please review current head f94b34d for convergence. The latest commit pins exact verifier head/bundle/signal inputs, exposes an active-head envelope at the candidate boundary, and verifies full multi-subject handoff; Agent build/type/package checks and 65/65 focused tests pass.

[Jurij89]

@otReviewAgent Please review the current head after the empty retrigger commit; evaluate the exact active receiver kernel for convergence.