fix: save checkpoint immediately after file read operations

- Add checkpoint save after read_file tool execution
- Ensures context is preserved when files are read for the first time
- Fixes issue where checkpoints were only saved after command execution

Fixes #9679

src/core/assistant-message/presentAssistantMessage.ts

@@ -852,6 +852,8 @@ export async function presentAssistantMessage(cline: Task) {
 							toolProtocol,
 						})
 					}
+					// Save checkpoint after reading files to preserve context
+					await checkpointSaveAndMark(cline)
 					break
 				case "fetch_instructions":
 					await fetchInstructionsTool.handle(cline, block as ToolUse<"fetch_instructions">, {