fix(aclk): prevent unbounded one-core CPU spins in the cloud-connection loops - #22879

sequenceDiagram
    participant Agent as Agent Main
    participant ACLK as ACLK Sync Loop
    participant JudyL as JudyL Queue
    participant MQTT as MQTT WSS Client
    participant HTTPS as HTTPS Client
    participant Cloud as Cloud Endpoint
    participant poll as poll() syscall

    Note over Agent,Cloud: ACLK Sync Loop – Query Dispatch (no-progress spin fix)

    loop Each iteration
        ACLK->>JudyL: dequeue next opcode
        alt opcode == ACLK_DATABASE_NOOP and pending_queries > 0
            ACLK->>JudyL: NEW: reconcile pending_queries with JudyLCount()
            alt pending_queries != JudyLCount()
                ACLK->>ACLK: NEW: log rate-limited warning, set pending_queries = JudyLCount()
            end
            ACLK->>ACLK: if pending_queries > 0 and queries_running < limit → rewrite to ACLK_QUERY_EXECUTE
        else opcode == ACLK_QUERY_EXECUTE
            ACLK->>JudyL: process query, decrement pending_queries
        end
    end

    Note over MQTT,Cloud: MQTT WSS Service – I/O Handling (watchdog + error check)

    MQTT->>poll: poll() with timeout
    alt poll() returns 0 (clean timeout)
        MQTT->>MQTT: NEW: update last_io_progress_ut
        MQTT->>MQTT: handle keepalive
    else poll() returns >0 (readiness)
        Note over MQTT: NEW: no-progress watchdog (only for established connection)
        MQTT->>MQTT: check revents for POLLERR | POLLNVAL
        alt revents matches error
            MQTT->>MQTT: NEW: return MQTT_WSS_ERR_CONN_DROP (break spin)
        else revents not error
            MQTT->>MQTT: check if no progress for MQTT_WSS_IO_WATCHDOG_SECS
            alt watchdog elapsed
                MQTT->>MQTT: NEW: return MQTT_WSS_ERR_CONN_DROP (break spin)
            end
            MQTT->>Cloud: attempt SSL read/write
            alt bytes moved
                MQTT->>MQTT: NEW: update last_io_progress_ut
            else SSL error
                MQTT->>MQTT: existing error handling
            end
        end
    end

    Note over HTTPS,Cloud: HTTPS Client Poll Loops (timeout check on every iteration)

    HTTPS->>HTTPS: enter write or read loop (socket_write_all / ssl_write_all / read_parse_response)
    loop Until I/O complete or error
        HTTPS->>HTTPS: NEW: check https_req_check_timedout()
        alt timed out
            HTTPS->>HTTPS: NEW: return timeout (break unbounded spin)
        else not timed out
            HTTPS->>poll: poll() with timeout
            alt poll() > 0 (ready)
                HTTPS->>Cloud: perform underlying I/O (send/recv)
                alt I/O progressed
                    HTTPS->>Cloud: continue loop
                else I/O error
                    HTTPS->>HTTPS: existing error handling
                end
            else poll() == 0 (timeout)
                HTTPS->>HTTPS: existing timeout handling (now also covered by top check)
            end
        end
    end

sequenceDiagram
    participant SyncLoop as ACLK Sync Event Loop
    participant Judy as JudyL Query Queue
    participant Counter as pending_queries
    participant MQTT as MQTT WSS Client
    participant Poll as poll/SSL
    participant HTTPS as HTTPS Client
    participant Timeout as Request Timeout

    Note over SyncLoop,Judy: ACLK Sync Dispatch Loop (sqlite_aclk.c)

    loop Each iteration
        SyncLoop->>Counter: Read pending_queries
        alt opcode == ACLK_DATABASE_NOOP
            SyncLoop->>Judy: NEW: JudyLCount() – source of truth
            Judy-->>SyncLoop: queued count
            alt queued != pending_queries
                SyncLoop->>SyncLoop: NEW: log discrepancy, set pending_queries = queued
            end
        end
        alt pending_queries > 0 and slots available
            SyncLoop->>SyncLoop: Rewrite NOOP → ACLK_QUERY_EXECUTE
            SyncLoop->>Judy: Pop and dispatch query
        end
    end

    Note over MQTT,Poll: MQTT WSS Service (mqtt_wss_client.c)

    MQTT->>MQTT: On CONNACK – NEW: seed last_io_progress_ut
    loop mqtt_wss_service entered periodically
        MQTT->>Poll: poll(timeout_ms)
        alt poll returns 0
            MQTT->>MQTT: NEW: update last_io_progress_ut (clean idle)
            MQTT->>MQTT: Handle keepalive if needed
        else poll returns >0
            MQTT->>MQTT: NEW: check revents & POLLERR|POLLNVAL
            alt error present
                MQTT->>MQTT: Drop connection, return MQTT_WSS_ERR_CONN_DROP
            else
                MQTT->>MQTT: NEW: check watchdog (elapsed > 2*PING_TIMEOUT?)
                alt time exceeded
                    MQTT->>MQTT: Drop connection, return MQTT_WSS_ERR_CONN_DROP
                else
                    MQTT->>Poll: SSL_read / SSL_write
                    alt bytes transferred
                        MQTT->>MQTT: NEW: update last_io_progress_ut
                    end
                end
            end
        end
    end

    Note over HTTPS,Timeout: HTTPS Client Poll Loops (https_client.c)

    loop socket_write_all / ssl_write_all / read_parse_response
        HTTPS->>Timeout: NEW: https_req_check_timedout() on every iteration
        alt timed out
            HTTPS->>HTTPS: Return error (2 or HTTPS_CLIENT_RESP_TIMEOUT)
        else
            HTTPS->>Poll: poll(POLL_TO_MS)
            alt poll > 0
                HTTPS->>Poll: Read/write data
            else poll error
                HTTPS->>HTTPS: Handle poll error
            end
        end
    end