Switch support agent to mqtt

[cstns]

Description

This PR switches the Expert assistant's communication layer from HTTP to MQTT for real-time bidirectional messaging, gated behind a PostHog feature flag (isExpertCommsBetaEnabled). It also introduces admin UI for managing Expert agent MQTT broker credentials, improves contextual awareness across the app, and refactors several UI components.

MQTT Communication Layer

• New MqttExpertTopicHelper composable: builds and parses structured MQTT topic paths (ff/v1/expert/<userId>/<sessionId>/<entityType>/<entityId>/<agentChannel>/<topicType>/<topicAction>) with full entity type resolution (application, instance, device, team).
• Enhanced MqttService: adds disconnect, end, reconnect, packetsend, packetreceive, and outgoingEmpty event handlers; introduces reconnectGeneration to prevent stale reconnect timers from firing; adds _killStaleClient for forceful cleanup of zombie MQTT clients; fixes reconnect guard to skip when already connected/connecting; adds connectHandlerPromise to serialize connect handler work and prevent publish before subscribe races; switches internal _ helpers to private; sets keepalive: 45; adds normalized reconnect policy defaults.
• Categorized MQTT error codes: exported sets for FATAL_ERROR_CODES, TRANSIENT_ERROR_CODES, THROTTLED_ERROR_CODES, PROTOCOL_BUG_ERROR_CODES, and ERRORS_WITHOUT_CODES to drive user facing error messaging with context appropriate language.

Expert Store (product-expert.js)

• Dual transport (sendQuery): routes through sendMqttQuery or sendHttpQuery based on the feature flag.
• MQTT lifecycle management: establishMqttComms creates a keyed MQTT client with dynamic credentials from userApi.initiateExpertChat; topic subscriptions happen in _onMqttConnect using wildcard patterns; _onMqttMessage dispatches to handleMessageResponse (chat replies) or handleInFlightRequest (tool call in flight requests).
• In flight request tracking: tracks pending MQTT requests per agent store; handles expert:status-message (acks) and automation:* (proxied to Node RED via invokeActionAwaitResponse) in flight request types.
• Error handling with personality: randomized, user friendly error and reconnection messages with duplicate error suppression based on recent error codes.
• stopInflightChat: clears in flight requests and updates when the user cancels mid flight.
• inFlightUpdates: surfaces real time tool call status/tool name updates to the loading indicator.

Product Assistant Store

• invokeActionAwaitResponse: new method that sends a postMessage to the immersive editor iframe and returns a promise that resolves when the correlated response arrives (or rejects after timeout); uses pendingRequests map keyed by composite sessionId:chatTransactionId:transactionId.
• isImmersiveInstance / isImmersiveDevice getters: replace the old immersiveInstance/immersiveDevice getters to require both entity presence and immersive mode, fixing false positive immersive detection.
• targetOrigin fix: uses contextStore directly instead of the old getters for postMessage target origin.

Context Store & Mixins

• isImmersive flag: added to the context store, set/cleared by Instance and Device editors on mount/unmount.
• application in context: new setApplication action; Application mixin now writes the contextual application into the store (and clears on unmount).
• Device/Instance mixins: set contextual entities on mount/watch and clear on unmount for consistent contextual awareness.

Admin UI: Expert Agent Credentials

• Generate/delete MQTT broker credentials for the Expert agent in Admin > Settings > General (only visible when isExpertCommsBetaEnabled flag is active).
• New API functions: adminApi.generateExpertAgentCreds() / adminApi.deleteExpertAgentCreds() and userApi.initiateExpertChat().

Infrastructure

• projectCount cast to integer in ProjectTemplate DB views to fix data type inconsistency.

UI Improvements

• ToolCallItem extracted into its own Vue component from ToolCalls, with collapsed list limited to 2 items and scrollable/expandable tool list (max 5 collapsed, 15 expanded).
• Tool call duration moved into the tool call title row; status prioritized over tool name.
• Code block styling: removed border/padding from agent response code blocks; improved markdown table styling.
• Chat input overflow fix: prevents context selection pills from overflowing the input area.
• Download chat messages: hidden Shift+Alt+D keyboard shortcut to download expert messages as JSON.
• Simplified hydrateMessages: cleaner switch based logic since tool calls aren't received when ingesting website context.
• StreamableContent: rendering support for streamable content blocks.

Caution

Changes made in .github/workflows/branch-deploy.yaml and ci/ci-values.yaml files are exclusive to this pull request and should be reverted before merge.

Related Issue(s)

closes #6972

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.59%. Comparing base (b3a1c78) to head (617bb17).
⚠️ Report is 29 commits behind head on main.

Files with missing lines	Patch %	Lines
forge/db/views/ProjectTemplate.js	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7090   +/-   ##
=======================================
  Coverage   76.58%   76.59%           
=======================================
  Files         405      405           
  Lines       20580    20579    -1     
  Branches     4974     4975    +1     
=======================================
  Hits        15762    15762           
+ Misses       4818     4817    -1     

Flag	Coverage Δ
backend	76.59% <0.00%> (+<0.01%)	⬆️

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[cstns]

ready for review, leaving it as draft for the time being because we still need to remove the ci bits that enabled testing on pre-staging

[Steve-Mcl]

Acknowledging this is a large PR (unavoidable mostly) but also acknowledging it has been dogfooded by 3 team members over last week it is good to go AFTER CI stuff is deleted.

[Steve-Mcl]

Suggested change

// console.debug('Received response for in-flight request:', { correlationId, originalRequest: inflight.postMessagePayload, response: payloadData })