Refactor span error recording into tracing helper and unify error-path instrumentation

[Copilot]

This change addresses duplicated OpenTelemetry error instrumentation (RecordError + SetStatus) across server/tool execution and HTTP tracing paths. It centralizes the pattern in one helper to keep behavior consistent and eliminate drift (including the rate-limit path that previously missed stack-trace recording).

• Centralize span error instrumentation

  • Added internal/tracing/span_helpers.go with:
    • RecordSpanError(span, err, msg)
  • Helper records the error with stack trace and sets span status in one call.

• Replace duplicated call sites in unified tool flow

  • Updated internal/server/unified.go to use tracing.RecordSpanError(...) for:
    • tool not allowed
    • tool call limit reached
    • DIFC access denied
    • circuit breaker open
    • tool execution failed
    • rate-limit exceeded on both execSpan and toolSpan

• Apply same helper in HTTP 5xx tracing

  • Updated internal/tracing/http.go so 5xx response handling uses the same helper, aligning server-span behavior with tool-span behavior.

• Tighten behavior assertion for 5xx spans

  • Updated internal/tracing/provider_test.go to assert 5xx spans include an exception event with exception.stacktrace, ensuring helper-backed semantics are preserved.

// internal/tracing/span_helpers.go
func RecordSpanError(span oteltrace.Span, err error, msg string) {
	span.RecordError(err, oteltrace.WithStackTrace(true))
	span.SetStatus(codes.Error, msg)
}

[lpcox]

@copilot resolve the merge conflicts in this pull request

[Copilot]

Pull request overview

This PR centralizes OpenTelemetry span error instrumentation by introducing a helper that consistently records errors (with stack traces) and sets span status, then updates tool execution and HTTP tracing paths to use it.

Changes:

• Added tracing.RecordSpanError(...) (and a multi-span variant) to unify RecordError + SetStatus behavior.
• Refactored unified tool execution error paths to use the helper (including rate-limit paths across multiple spans).
• Updated HTTP 5xx span handling to use the helper and tightened tests to assert exception stack traces are present.

Show a summary per file

File	Description
internal/tracing/span_helpers.go	Introduces helper(s) to record span errors with stack traces and set error status consistently.
internal/server/unified.go	Replaces duplicated error instrumentation across tool execution error paths with the new helper(s).
internal/tracing/http.go	Uses the helper to record 5xx responses as span errors (exception event + status).
internal/tracing/provider_test.go	Strengthens 5xx tracing assertions to require an exception event containing a stack trace attribute.

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• Files reviewed: 2/2 changed files
• Comments generated: 1

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved. This branch already contains the merge commit c56cbfe from main, and I re-fetched origin/main and confirmed it is up to date and conflict-free.

[lpcox]

@copilot address review feedback

[Copilot]

@copilot address review feedback

Addressed in 541d061. Added a fallback for unknown/custom 5xx status text in internal/tracing/http.go (HTTP <code> when http.StatusText is empty) and added a regression test TestWrapHTTPHandler_Unknown5xxUsesFallbackStatusDescription in internal/tracing/provider_test.go.