fix(app): wire signal-aware context through controller startup

[SarthakB11]

summary

• app.Start constructed two independent signal-handling setups: an early ctx := context.Background() used for tracing init and db connect, and a separate ctrl.SetupSignalHandler() passed to mgr.Start later. controller-runtime requires the signal handler be set up exactly once per process, so the second call is a latent panic risk if a future caller adds another signal-handler setup. addresses the long-standing // TODO setup signal handlers at go/core/pkg/app/app.go:297.
• call ctrl.SetupSignalHandler() once at the top of Start and reuse the returned context for both startup work and mgr.Start. tracing init, db connect, and the manager now share a single signal-aware ctx; the duplicate setup is gone.
• note: the default migration runner (app.go:462) discards its ctx argument and migrations.RunUp does not accept ctx, so migrations themselves are still not cancellable by this PR. threading ctx through migrations.RunUp is a separate change; happy to follow up.

ai model disclosure

used claude code (claude opus 4.7) to triage and draft the diff. self-reviewed go/core/pkg/app/app.go to confirm the second ctrl.SetupSignalHandler() call site at line 670 and the manager's downstream use of ctx. verified locally via:

go vet ./core/pkg/app/...
./bin/golangci-lint run ./core/pkg/app/...      # 0 issues
go test -race -skip 'TestE2E.*' -count=1 ./core/pkg/app/...   # ok

[Copilot]

Pull request overview

This PR ensures the controller’s startup path uses the same signal-aware context as mgr.Start, so SIGTERM during early initialization (tracing init, migrations, DB connect, etc.) can propagate cancellation and avoid hanging past Kubernetes termination grace periods. It also eliminates a second ctrl.SetupSignalHandler() call to align with controller-runtime’s “call once per process” requirement.

Changes:

• Initialize a single signal-aware ctx via ctrl.SetupSignalHandler() at the top of app.Start.
• Reuse that ctx throughout startup and pass it into mgr.Start instead of creating a second signal handler.

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[SarthakB11]

good catch. you're right, the default runner at app.go:462 takes _ context.Context and migrations.RunUp doesn't accept ctx at all, so migrations aren't cancellable by this PR.

I have updated the description, this PR only makes tracing init, db connect, and the manager signal-aware, plus removes the duplicate ctrl.SetupSignalHandler() call. threading ctx through migrations.RunUp is a separate change. happy to open a follow-up if maintainers want it.