feat: [AI-6771] add telemetry for streaming error scenarios

[altimate-harness-bot]

Summary

• Add Telemetry.track({ type: "error", context: "streaming" }) in the non-retry, non-overflow branch of processor.ts streaming catch block
• Covers MessageAbortedError (Stop/dispose), UnknownError (SSE chunk timeout after retry exhaustion), APIError (provider failures), AuthError, and any other unhandled streaming error
• Event fields: session_id, error_name, error_message, context: "streaming"

Context

Previously, streaming errors in the catch block of SessionProcessor.process() were published to Bus.publish(Session.Event.Error) but not tracked as telemetry events. This means SSE chunk timeouts, provider failures after retry exhaustion, and unexpected streaming errors were invisible in dashboards.

The change fires Telemetry.track({ type: "error", ... }) after Bus.publish in the non-retry, non-overflow branch only:

• Context overflow: tracked separately by context_overflow_recovered
• Retryable errors: tracked as error_recovered events on each retry
• Stop/abort: intentional — covered by agent_outcome: aborted at session level
• This change: the "give up" path — non-retryable errors or retry exhaustion

Test plan

• TypeScript typecheck passes (bun run --cwd packages/opencode turbo typecheck)
• Verify event fires: trigger a streaming error (e.g., revoke API key mid-session, network drop) and confirm error event with context: "streaming" appears in App Insights

Requested by @saravmajestic via harness

Jira: AI-6771

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Summary by cubic

Add telemetry for unhandled streaming errors in SessionProcessor.process() so we can see failures that aren’t retried or context overflows. Emits Telemetry.track({ type: "error", context: "streaming" }) with session_id, error_name, and error_message after the bus publish, covering SSE timeouts, provider/auth failures, and aborts; addresses AI-6771.

^{Written for commit 36b2390. Summary will update on new commits. Review in cubic}

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[altimate-harness-bot]

Folded into #845