[tomr-fly]

Include the acquired Depot builder target and connection stage in build reports so web can resolve the builder region and group failures. Preserve useful error details and give canceled builds a bounded chance to report.

[Copilot]

🟡 Changes recommended

Resolve the critical finish-context deadline issue and the moderate error-classification and configuration-retry issues before approval.

2 open issues

• Preserve parent deadline for non-cancellation build failures · New
• Classify wrapped gRPC cancellation and deadline errors · New

What changed in this PR

This pull request adds Depot builder routing and connection diagnostics to build reports, including failure details and bounded reporting after cancellation.

Changes:

• Adds Depot acquisition target, connection stage, and outcome metadata.
• Adds readiness retries, error preservation, and connection classification.
• Adds cancellation handling and telemetry tests.

File	Summary
internal/​uiex/​builders.go	Adds Depot telemetry fields to builder metadata.
internal/​build/​imgsrc/​resolver.go	Adds bounded context handling for failed Depot reports.
internal/​build/​imgsrc/​depot.go	Records the acquired target and connection stages.
internal/​build/​imgsrc/​depot_test.go	Tests acquisition metadata privacy on failure.
internal/​build/​imgsrc/​depot_telemetry_test.go	Tests telemetry, retries, cancellation, and failure reporting.
internal/​build/​imgsrc/​depot_connection.go	Implements readiness retries and connection error classification.
go.mod	Promotes protobuf to a direct dependency for test utilities.

_{Review effort: Lite}