feat(ws): add result-channel output streaming, ACK handling, and replay

[iAziz786]

Summary

Add result-channel capabilities to the existing HTTP-polling task runner and WebSocket client so task output and final results stream over the authenticated agent WebSocket with durable ACK handling. HTTP final reporting is preserved as fallback when WebSocket delivery is unavailable.

New files

• app/jobs/taskjob/result_channel_test.go — tests for result-channel streaming, HTTP fallback, throttled capture, retryable error handling

Modified files

• app/jobs/taskjob/taskjob.go — add ResultChannel interface, processTaskWithResultChannel for stdout/stderr pipe capture with interval/byte-threshold flush, final persistence before send, HTTP fallback
• app/services/wsclient/client.go — add SendOutput/SendFinal methods, replayUnacked after hello_ack, ACK-driven outbox removal, write-mutex serialization
• app/services/wsclient/client_test.go — tests for ack outbox removal, reconnect replay, retryable error handling
• domain/task/task.go — add ExecutionAttemptID field to domain task
• internal/wsprotocol/ack_sequence.go — add HighestAcceptedSequence to ErrorPayload/ErrorOptions
• internal/wsprotocol/ack_sequence_test.go — update error payload tests
• main.go — wire local store as result outbox into WebSocket client; pass result channel to task job

Key design decisions

• Output persists to local outbox before WebSocket send (durable before deliver)
• Throttle flushed on configurable interval (100ms) or byte threshold (16KB)
• ACK removes exact message_id from outbox; retryable errors keep messages
• Replay of unacked output/final messages after agent.hello_ack preserves original IDs/sequences
• HTTP fallback fires when final persistence fails or WS is not configured
• Write mutex prevents ping/replay/live-send races on the Gorilla websocket