Handle SIGINT/SIGTERM to allow graceful shutdown (#28)

## Problem

The breakpoint CLI ignored interrupt signals (SIGINT/SIGTERM) because
the root context was a plain `context.Background()` with no signal
handling. This meant Ctrl+C and GitHub Actions cancellation had no
effect — the process would keep running until the timer expired.

## Fix

Use `signal.NotifyContext` in `main.go` to cancel the root context on
SIGINT and SIGTERM. This propagates through all subcommands (`wait`,
`hold`, etc.) via their `<-ctx.Done()` selects.

Co-authored-by: Amp <amp@ampcode.com>

Author: annervisser

.github/workflows/build.yml

@@ -46,5 +46,5 @@ jobs:
           SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
         with:
           duration: 30m
-          authorized-users: edganiukov,hugosantos,n-g,htr,nichtverstehen,gmichelo
+          authorized-users: hugosantos,n-g,htr
           slack-announce-channel: "#ci"

.github/workflows/checks.yml

@@ -40,5 +40,5 @@ jobs:
           SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
         with:
           duration: 30m
-          authorized-users: edganiukov,hugosantos,n-g,htr,nichtverstehen,gmichelo
+          authorized-users: hugosantos,n-g,htr
           slack-announce-channel: "#ci"

.github/workflows/release.yml

@@ -46,5 +46,5 @@ jobs:
           SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
         with:
           duration: 30m
-          authorized-users: edganiukov,hugosantos,n-g,htr,nichtverstehen,gmichelo
+          authorized-users: hugosantos,n-g,htr
           slack-announce-channel: "#ci"

cmd/breakpoint/main.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"os/signal"
+	"syscall"
 
 	"github.com/spf13/cobra"
 	"namespacelabs.dev/breakpoint/pkg/blog"
@@ -20,7 +22,10 @@ func main() {
 
 	l := blog.New()
 
-	err := rootCmd.ExecuteContext(l.WithContext(context.Background()))
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+
+	err := rootCmd.ExecuteContext(l.WithContext(ctx))
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)