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 ./...

3 files changed, 26 insertions, 19 deletions

diff --git a/internal/processor/markdown_test.go b/internal/processor/markdown_test.go
index c53874d..b4582a9 100644
--- a/internal/processor/markdown_test.go
+++ b/internal/processor/markdown_test.go
@@ -1,6 +1,7 @@
 package processor
 
 import (
+	"context"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -121,7 +122,6 @@ func TestFindLocalImages(t *testing.T) {
 			want:    []string{"z.gif"},
 			wantLen: 1,
 		},
-
 	}
 
 	for _, tt := range tests {
@@ -178,7 +178,7 @@ func TestRun_UnreadableMarkdownPreScanFails(t *testing.T) {
 	t.Cleanup(func() { _ = os.Chmod(mdPath, 0o644) })
 
 	cfg := &config.Config{InputDir: inputDir, OutputDir: outputDir}
-	_, err := Run(cfg)
+	_, err := Run(context.Background(), cfg)
 	if err == nil {
 		t.Fatal("Run: expected error when markdown pre-scan cannot read a .md file")
 	}
diff --git a/internal/processor/processor.go b/internal/processor/processor.go
index bb3a84d..0bbc28e 100644
--- a/internal/processor/processor.go
+++ b/internal/processor/processor.go
@@ -4,9 +4,10 @@
 // Each processed source file is deleted from the input directory afterward.
 //
 // Processing uses a two-phase commit pattern:
-//   1. Scan and validate every inbox item without mutating anything.
-//   2. Only after all items pass validation, execute mutations
-//      (create directories, write assets, persist posts, remove sources).
+//  1. Scan and validate every inbox item without mutating anything.
+//  2. Only after all items pass validation, execute mutations
+//     (create directories, write assets, persist posts, remove sources).
+//
 // If validation fails for any item, the entire batch is aborted and the inbox
 // is left untouched. If a mutation fails mid-batch, earlier items have already
 // been committed; the failing item is rolled back and the error is returned
@@ -21,6 +22,7 @@
 package processor
 
 import (
+	"context"
 	"fmt"
 	"image"
 	"os"
@@ -38,7 +40,7 @@ import (
 // to the core planning or commit loops are required.
 type PostBuilder interface {
 	// Plan validates the source file and returns everything needed to commit it later.
-	 Plan(srcPath string, ext string) (postPlan, error)
+	Plan(srcPath string, ext string) (postPlan, error)
 	// Commit performs the mutations for this post type and returns the populated Post,
 	// plus any extra inbox files that should be cleaned up after a successful save.
 	Commit(plan postPlan, postDir string, id string, now time.Time) (*post.Post, []string, error)
@@ -60,13 +62,15 @@ func register(ext string, b PostBuilder) {
 // Run scans cfg.InputDir and processes every eligible file into a post directory
 // under cfg.OutputDir/posts/. It uses a two-phase commit pattern:
 //
-//   Phase 1 — scan and validate all inbox items without mutating anything.
-//   Phase 2 — only after all items pass validation, execute mutations
-//             (create directories, write assets, persist posts, remove sources).
+//	Phase 1 — scan and validate all inbox items without mutating anything.
+//	Phase 2 — only after all items pass validation, execute mutations
+//	          (create directories, write assets, persist posts, remove sources).
 //
 // If Phase 1 fails for any item, no mutations occur and the inbox is left untouched.
 // Returns the number of posts successfully created in this invocation.
-func Run(cfg *config.Config) (int, error) {
+// The ctx parameter is accepted for cancellation propagation; it is currently
+// wired through for API consistency.
+func Run(ctx context.Context, cfg *config.Config) (int, error) {
 	entries, err := os.ReadDir(cfg.InputDir)
 	if err != nil {
 		return 0, fmt.Errorf("read input dir %s: %w", cfg.InputDir, err)
diff --git a/internal/processor/processor_test.go b/internal/processor/processor_test.go
index 418fb95..b5e8f20 100644
--- a/internal/processor/processor_test.go
+++ b/internal/processor/processor_test.go
@@ -1,6 +1,7 @@
 package processor
 
 import (
+	"context"
 	"image"
 	"image/png"
 	"os"
@@ -13,6 +14,8 @@ import (
 	"codeberg.org/snonux/snonux/internal/post"
 )
 
+var ctx = context.Background() //nolint:gochecknoglobals // test-only top-level helper used by every test in the file
+
 func TestRun_processesTxt(t *testing.T) {
 	t.Parallel()
 
@@ -23,7 +26,7 @@ func TestRun_processesTxt(t *testing.T) {
 	}
 
 	cfg := &config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x.test"}
-	n, err := Run(cfg)
+	n, err := Run(ctx, cfg)
 	if err != nil {
 		t.Fatalf("Run: %v", err)
 	}
@@ -57,7 +60,7 @@ func TestRun_unsupportedExt(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	_, err := Run(&config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
+	_, err := Run(ctx, &config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
 	if err == nil {
 		t.Fatal("expected error")
 	}
@@ -66,7 +69,7 @@ func TestRun_unsupportedExt(t *testing.T) {
 func TestRun_readInputDirFails(t *testing.T) {
 	t.Parallel()
 
-	_, err := Run(&config.Config{InputDir: "/nonexistent/inbox/xyz", OutputDir: t.TempDir(), BaseURL: "https://x"})
+	_, err := Run(ctx, &config.Config{InputDir: "/nonexistent/inbox/xyz", OutputDir: t.TempDir(), BaseURL: "https://x"})
 	if err == nil {
 		t.Fatal("expected error")
 	}
@@ -89,7 +92,7 @@ func TestRun_png(t *testing.T) {
 	}
 	f.Close()
 
-	n, err := Run(&config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
+	n, err := Run(ctx, &config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
 	if err != nil {
 		t.Fatalf("Run: %v", err)
 	}
@@ -107,7 +110,7 @@ func TestRun_mp3(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	n, err := Run(&config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
+	n, err := Run(ctx, &config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
 	if err != nil {
 		t.Fatalf("Run: %v", err)
 	}
@@ -125,7 +128,7 @@ func TestRun_markdown(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	n, err := Run(&config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
+	n, err := Run(ctx, &config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
 	if err != nil {
 		t.Fatalf("Run: %v", err)
 	}
@@ -216,7 +219,7 @@ text`
 		t.Fatal(err)
 	}
 
-	n, err := Run(&config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
+	n, err := Run(ctx, &config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
 	if err != nil {
 		t.Fatalf("Run: %v", err)
 	}
@@ -264,7 +267,7 @@ func TestRun_twoMarkdownsClaimingSameImageFails(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	_, err = Run(&config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
+	_, err = Run(ctx, &config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
 	if err == nil {
 		t.Fatal("expected error when two markdowns claim the same image")
 	}
@@ -307,7 +310,7 @@ func TestRun_duplicateImageClaimsInSameMarkdownAllowed(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	n, err := Run(&config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
+	n, err := Run(ctx, &config.Config{InputDir: in, OutputDir: out, BaseURL: "https://x"})
 	if err != nil {
 		t.Fatalf("Run: %v", err)
 	}