feat(ai) - add light AI chat turn instrumentation (metrics + Sentry correlation) (#22692)

## Summary

Adds minimal server-side observability for AI chat turns: lifecycle
counters to measure success/failure rates, Sentry scope tags to
correlate API and worker traces, and per-LLM-call telemetry metadata for
turn/stream correlation.

- Add turn lifecycle metrics: `ai-chat/turn-started`,
`ai-chat/turn-completed`, `ai-chat/turn-failed` (with `failure_phase`
and `error_code` attributes)
- Emit counters at key points: job start, clean completion, execution
failures, enqueue failures, interrupted streams, and empty completions
- Tag Sentry scope with `streamId`, `turnId`, `threadId`, and
`workspaceId` at API entry points (`sendChatMessage`,
`retryChatMessage`, `answerAgentChatQuestion`) and worker entry
(`StreamAgentChatJob`)
- Enrich LLM `experimental_telemetry` metadata with
stream/turn/thread/workspace IDs
- Return `turnId` from streaming service methods so resolvers can tag
the scope
- Remove granular tool-learned/skill-loaded metrics in favor of the
turn-level counters

## Test plan

- [ ] Send a chat message and verify `ai-chat/turn-started` and
`ai-chat/turn-completed` increment
- [ ] Trigger a stream failure (e.g. interrupted/dead stream) and verify
`ai-chat/turn-failed` with correct `failure_phase`
- [ ] Retry a failed turn and confirm a new `turn-started` is emitted
for the retry attempt
- [ ] Answer an `ask_questions` prompt and confirm Sentry tags include
`streamId` and `turnId`
- [ ] Check Sentry spans for LLM calls include `streamId`, `turnId`,
`threadId`, `workspaceId` in telemetry metadata
- [ ] Run unit tests:
- `npx jest
packages/twenty-server/src/engine/metadata-modules/ai/ai-chat/jobs/__tests__/stream-agent-chat.job.spec.ts`
- `npx jest
packages/twenty-server/src/engine/metadata-modules/ai/ai-chat/services/__tests__/agent-chat-streaming.service.claim.spec.ts`
- `npx jest
packages/twenty-server/src/engine/metadata-modules/ai/ai-chat/services/__tests__/agent-chat-streaming.service.retry.spec.ts`

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packages/twenty-server/src/engine/core-modules/metrics/types/metrics-keys.type.ts

@@ -25,10 +25,6 @@ export enum MetricsKeys {
   WorkflowRunSystemError = 'workflow-run/system-error',
   AiChatToolExecutionSucceeded = 'ai-chat/tool-execution-succeeded',
   AiChatToolExecutionFailed = 'ai-chat/tool-execution-failed',
-  AiChatToolLearnedSucceeded = 'ai-chat/tool-learned-succeeded',
-  AiChatToolLearnedFailed = 'ai-chat/tool-learned-failed',
-  AiChatSkillLoadedSucceeded = 'ai-chat/skill-loaded-succeeded',
-  AiChatSkillLoadedFailed = 'ai-chat/skill-loaded-failed',
   WorkflowAgentToolExecutionSucceeded = 'workflow-agent/tool-execution-succeeded',
   WorkflowAgentToolExecutionFailed = 'workflow-agent/tool-execution-failed',
   McpToolExecutionSucceeded = 'mcp/tool-execution-succeeded',
@@ -53,5 +49,8 @@ export enum MetricsKeys {
   AiChatTurnLatencyMs = 'ai-chat/turn-latency-ms',
   AiChatStepLatencyMs = 'ai-chat/step-latency-ms',
   AiChatTtftMs = 'ai-chat/ttft-ms',
+  AiChatTurnStarted = 'ai-chat/turn-started',
+  AiChatTurnCompleted = 'ai-chat/turn-completed',
+  AiChatTurnFailed = 'ai-chat/turn-failed',
   WorkspaceMetadataCacheLocalEviction = 'workspace-metadata-cache/local-eviction',
 }