feat(proto): add RunnerService.CommitConversationFrame sink-ack RPC

[mattwilkinsonn]

What

Adds the CommitConversationFrame unary RPC to RunnerService (proto/compass/v1/runner.proto) plus its request/response messages, and regenerates the internal-go stubs. This is T1 of the agent↔runner sink-ack seam (closes #24 OQ-3).

• RPC (after RelayCommsCall): CommitConversationFrame(CommitConversationFrameRequest) returns (CommitConversationFrameResponse) — the Server-terminated half of the agent's PostConversationFrame. The Runner forwards a durable conversation frame here (rather than onto the loss-tolerable PublishEvents spine) and gets back the sink result, so a durable post resolves delivered-or-erred with real coordinates instead of fire-and-forget.
• CommitConversationFrameRequest { string session_id = 1; AgentFrame frame = 2; string idempotency_key = 3; } — mirrors PostConversationFrameRequest (same AgentFrame + agent-minted idempotency_key envelope-dedup field), plus an explicit session_id because on the Runner→Server hop there is no per-container socket to carry session identity. The Runner asserts no account; the Server resolves session_id → account from its own binding, fail-closed CodeNotFound, same posture as RelayCommsCall.
• CommitConversationFrameResponse { bool committed = 1; string message_id = 2; uint64 seq = 3; } — the sink ack: message_id + seq are the durable coordinates the Server's commsConversationSink (CommitAgentPost/CommitAgentUpdate) assigns.

Naming note

The response type is ...Response, not ...Ack (as the seam spec sketched it): runner.proto keeps every STANDARD buf-lint rule armed, and RPC_RESPONSE_STANDARD_NAME requires the Response suffix. The only existing exemption (agent_gateway.proto's CommsCallResult) is justified by cross-hop envelope reuse, which this type does not have. The ack semantics live in the fields + doc-comment. Flagged to compass-server for confirmation.

Surface / safety

• Internal-go only. runner.proto generates solely into go/internal/gen (via buf.gen.internal-go.yaml); verified zero new surface in go/gen, the TS client, or the agent gen tree, so the @compass/client server-door fence holds.
• buf lint clean; buf breaking (glob compass/**/*.proto vs main) clean — purely additive in the owned compass.v1 package.
• Internal gen package builds (go build ./internal/gen/... rc=0).

Downstream (dogfood critical path)

Once merged: compass-server wires the Server handler (commsConversationSink → fills message_id/seq); compass-runner swaps its downstream PostConversationFrame from publisher.forward to this unary. Unblocks the C-series stack (#24 ← #38).

Refs SEA-1507

Co-Authored-By: seal noreply@sealedsecurity.com

[mattwilkinsonn]

• feat(proto): add RunnerService.CommitConversationFrame sink-ack RPC #42 👈 (View in Graphite)
• main

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[linear-code]

SEA-1507