Serialize restore recovery and rebase manifest paths

internal/artifacts/paths.go

@@ -32,6 +32,7 @@ type SessionPaths struct {
 	PreviousArtifactsDir  string
 	ManifestPath          string
 	LockPath              string
+	RestoreMarkerPath     string
 }
 
 // SessionWorkDirForCampaign returns the canonical campaign-aware work directory for one session.
@@ -44,6 +45,12 @@ func SessionManifestPathForCampaign(rootDir, campaign, sessionID string) string
 	return filepath.Join(SessionWorkDirForCampaign(rootDir, campaign, sessionID), config.PathManifestFile)
 }
 
+// SessionRestoreMarkerPathForCampaign returns the durable recovery marker for
+// a restore that has started changing one session's local state.
+func SessionRestoreMarkerPathForCampaign(rootDir, campaign, sessionID string) string {
+	return filepath.Join(SessionWorkDirForCampaign(rootDir, campaign, sessionID), ".restore-incomplete.json")
+}
+
 // SessionRunsDirForCampaign returns the canonical runs directory for one session.
 func SessionRunsDirForCampaign(rootDir, campaign, sessionID string) string {
 	return filepath.Join(SessionWorkDirForCampaign(rootDir, campaign, sessionID), config.PathRunsDirSegment)
@@ -264,5 +271,6 @@ func buildSessionPathsFromRoot(workspaceRoot, campaign, sessionID, root string)
 		PreviousArtifactsDir:  filepath.Join(root, config.PathPreviousDirSegment, config.PathArtifactsDirSegment),
 		ManifestPath:          filepath.Join(root, config.PathManifestFile),
 		LockPath:              filepath.Join(root, config.PathLockFile),
+		RestoreMarkerPath:     filepath.Join(root, ".restore-incomplete.json"),
 	}
 }