Fix TypeScript errors and ESLint warnings in checkpoint services

Author: bramburn

src/services/checkpoints/MigrationService.ts

@@ -86,7 +86,7 @@ export class MigrationService {
 
 			// Get commit history
 			const log = await git.log()
-			const commits = log.all.reverse() // Oldest first
+			const commits = [...log.all].reverse() // Oldest first
 
 			if (commits.length === 0) {
 				this.log(`[MigrationService#migrateTask] no commits found for task ${taskId}, skipping`)

src/services/checkpoints/PatchCheckpointService.ts

@@ -301,6 +301,11 @@ export class PatchCheckpointService extends EventEmitter {
 			from = this.baseSnapshot
 		}
 
+		// Ensure from is defined (TypeScript safety)
+		if (!from) {
+			throw new Error("Unable to determine source checkpoint")
+		}
+
 		// Get the source state
 		const sourceState =
 			from === this.baseSnapshot ? await this.getBaseSnapshotState() : await this.getCheckpointState(from)