fix(core): Release LS trace clients on run finalization (no-changelog)

[OlegIvaniv]

Summary

The module-level traceClients Map in langsmith-tracing.ts was only cleaned when a root run finished successfully via finishRun(). If a run was aborted, timed out, or the finishRun HTTP call failed, the Client and its entire RunTree hierarchy stayed in the Map indefinitely.

Add releaseTraceClient() that unconditionally deletes the entry, and call it from:

• finalizeMessageTraceRoot (normal message run completion)
• finalizeDetachedTraceRun (background task completion)
• deleteTraceContextsForThread (safety net on thread deletion)

Measured impact (parallel workflow building benchmark: 3 tabs × 3 rounds)

Metric	Before	After
Heap leak (post-cleanup − baseline)	+152 MB	+80 MB
Round-over-round growth (R2→R3)	+75 MB	+6 MB
RunTree objects after cleanup	127	near 0 (expected)

The remaining ~80 MB delta is one-time lazy loading (node type catalog, source maps, Zod schemas) that loads on first workflow build and stays flat across subsequent rounds.

Related Linear tickets, Github issues, and Community forum posts

Review / Merge checklist

• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.
• PR Labeled with Backport to Beta, Backport to Stable, or Backport to v1 (if the PR is an urgent fix that needs to be backported)
• I have seen this code, I have run this code, and I take responsibility for this code.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...cli/src/modules/instance-ai/instance-ai.service.ts	0.00%	3 Missing ⚠️

📢 Thoughts on this report? Let us know!

[cubic-dev-ai]

No issues found across 3 files

Architecture diagram

sequenceDiagram
    participant Svc as InstanceAiService
    participant Tracing as LangSmith Tracing Module
    participant Cache as traceClients (Map)
    participant LS as LangSmith API

    Note over Svc, LS: Run Finalization (Success or Failure)

    Svc->>Tracing: finalizeMessageTraceRoot / finalizeDetachedTraceRun
    
    rect rgb(240, 240, 240)
        Note right of Svc: try block
        Svc->>LS: finishRun (via SDK)
    end

    alt on Error
        LS-->>Svc: Error (Timeout/Network)
        Svc->>Svc: Log Error
    else on Success
        LS-->>Svc: 200 OK
    end

    Note right of Svc: finally block
    Svc->>Tracing: NEW: releaseTraceClient(traceId)
    Tracing->>Cache: NEW: delete(traceId)
    Note over Cache: GC can now reclaim Client<br/>and RunTree hierarchy

    Note over Svc, Cache: Thread Deletion (Safety Net)
    
    Svc->>Svc: deleteTraceContextsForThread(threadId)
    loop for each run context
        Svc->>Tracing: NEW: releaseTraceClient(traceId)
        Tracing->>Cache: NEW: delete(traceId)
    end

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