Integrate chunk plan caching into the runner

internal/core/workspace/manifest.go

@@ -11,7 +11,6 @@ type StageName string
 
 const (
 	StageSource    StageName = "source"
-	StageChunk     StageName = "chunk"
 	StageExtract   StageName = "extract"
 	StageMerge     StageName = "merge"
 	StageNormalize StageName = "normalize"
@@ -55,11 +54,6 @@ type SourceManifest struct {
 	SourceID string `json:"source_id,omitempty"`
 }
 
-type ChunkManifest struct {
-	StageManifest
-	ChunkCount int `json:"chunk_count,omitempty"`
-}
-
 type ExtractLaneManifest struct {
 	StageManifest
 	ChunkCount  int `json:"chunk_count,omitempty"`

internal/core/workspace/manifest_test.go

@@ -42,18 +42,6 @@ func TestManifestJSONRoundTrips(t *testing.T) {
 		}
 	})
 
-	t.Run("chunk", func(t *testing.T) {
-		manifest := ChunkManifest{
-			StageManifest: populatedManifest(StageChunk, "", "generic", started, completed),
-			ChunkCount:    3,
-		}
-		var got ChunkManifest
-		roundTripManifest(t, manifest, &got)
-		if got.ChunkCount != manifest.ChunkCount || got.Stage != StageChunk {
-			t.Fatalf("round trip chunk manifest = %+v", got)
-		}
-	})
-
 	t.Run("extract", func(t *testing.T) {
 		manifest := ExtractLaneManifest{
 			StageManifest: populatedManifest(StageExtract, "spells", "dnd/spells", started, completed),