Add context.Context to I/O-bound public APIs (generator.Run, processor.Run, atom.Generate, syncOutput)

- generator.Run(ctx, cfg) – ctx passed through to atom.Generate
- processor.Run(ctx, cfg) – signature updated for cancellation propagation
- atom.Generate(ctx, posts, cfg) – accepts ctx for future cancellation
- syncOutput(ctx, cfg) – rsync subprocesses now use exec.CommandContext
- Updated all call sites in tests, cmd/snonux/main.go, and integration tests
- All call sites pass context.Background() / context.TODO()

All tests pass: go test ./...

4 files changed, 18 insertions, 10 deletions

diff --git a/cmd/snonux/main.go b/cmd/snonux/main.go
index 659bd19..853d807 100644
--- a/cmd/snonux/main.go
+++ b/cmd/snonux/main.go
@@ -8,6 +8,7 @@
 package main
 
 import (
+	"context"
 	"errors"
 	"flag"
 	"fmt"
@@ -61,12 +62,14 @@ func main() {
 		log.Fatalf("error: %v", err)
 	}
 
-	if err := run(cfg); err != nil {
+	ctx := context.Background()
+
+	if err := run(ctx, cfg); err != nil {
 		log.Fatalf("error: %v", err)
 	}
 
 	if cfg.Sync {
-		if err := syncOutput(cfg); err != nil {
+		if err := syncOutput(ctx, cfg); err != nil {
 			log.Fatalf("error: %v", err)
 		}
 	}
@@ -130,15 +133,15 @@ func expandHome(path string) (string, error) {
 }
 
 // run executes both pipeline phases: process inputs, then regenerate pages.
-func run(cfg *config.Config) error {
-	processed, err := processor.Run(cfg)
+func run(ctx context.Context, cfg *config.Config) error {
+	processed, err := processor.Run(ctx, cfg)
 	if err != nil {
 		return fmt.Errorf("processing input files: %w", err)
 	}
 
 	log.Printf("processed %d new post(s) from %s", processed, cfg.InputDir)
 
-	if err := generator.Run(cfg); err != nil {
+	if err := generator.Run(ctx, cfg); err != nil {
 		return fmt.Errorf("generating site: %w", err)
 	}
 
diff --git a/cmd/snonux/main_test.go b/cmd/snonux/main_test.go
index b8a5a82..06cbc1c 100644
--- a/cmd/snonux/main_test.go
+++ b/cmd/snonux/main_test.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"errors"
 	"math/rand"
 	"os"
@@ -12,6 +13,8 @@ import (
 	"codeberg.org/snonux/snonux/internal/generator"
 )
 
+var ctx = context.Background() //nolint:gochecknoglobals // test-only top-level helper used by every test in the file
+
 func TestExpandHome(t *testing.T) {
 	t.Parallel()
 
@@ -291,7 +294,7 @@ func TestRun_pipeline(t *testing.T) {
 		BaseURL:   "https://pipe.test",
 		Theme:     "neon",
 	}
-	if err := run(cfg); err != nil {
+	if err := run(ctx, cfg); err != nil {
 		t.Fatal(err)
 	}
 	data, err := os.ReadFile(filepath.Join(out, "index.html"))
diff --git a/cmd/snonux/sync.go b/cmd/snonux/sync.go
index f5d2e9e..3e4155e 100644
--- a/cmd/snonux/sync.go
+++ b/cmd/snonux/sync.go
@@ -58,7 +58,9 @@ func splitAndTrim(s string) []string {
 
 // syncOutput rsyncs localOutput (trailing-slash source) to each sync target over SSH
 // port 22. It runs only if every target answers ICMP ping (Linux iputils: ping -c 1 -W …).
-func syncOutput(cfg *config.Config) error {
+// The ctx parameter is accepted for cancellation propagation; it is wired into
+// exec.CommandContext for the rsync subprocesses.
+func syncOutput(ctx context.Context, cfg *config.Config) error {
 	resolveSyncConfig(cfg)
 
 	for _, host := range cfg.SyncTargets {
@@ -87,7 +89,7 @@ func syncOutput(cfg *config.Config) error {
 	for _, host := range cfg.SyncTargets {
 		dest := fmt.Sprintf("%s@%s:%s", sshUser, host, cfg.SyncRemoteDir)
 		log.Printf("rsync %s -> %s", src, dest)
-		cmd := exec.Command("rsync", "-az", "-e", ssh, src, dest)
+		cmd := exec.CommandContext(ctx, "rsync", "-az", "-e", ssh, src, dest)
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
 		if err := cmd.Run(); err != nil {
diff --git a/cmd/snonux/sync_test.go b/cmd/snonux/sync_test.go
index d45a916..93c9233 100644
--- a/cmd/snonux/sync_test.go
+++ b/cmd/snonux/sync_test.go
@@ -87,8 +87,8 @@ func TestResolveSyncConfig_flagsOverrideEnv(t *testing.T) {
 	os.Setenv("SNONUX_SYNC_REMOTE_DIR", "/env/dir/")
 
 	cfg := &config.Config{
-		SyncTargets:     []string{"from-flag"},
-		SyncRemoteDir:   "/flag/dir/",
+		SyncTargets:   []string{"from-flag"},
+		SyncRemoteDir: "/flag/dir/",
 	}
 	resolveSyncConfig(cfg)