refactor: rename registerExecution to attachExecution for clarity

The "attach" verb makes it clear that the caller brings an existing
process/handle, while "create" (createExecution) means the lifecycle
service allocates and owns the execution from scratch.

packages/core/src/services/executionLifecycleService.test.ts

@@ -155,7 +155,7 @@ describe('ExecutionLifecycleService', () => {
     const chunks: string[] = [];
 
     let output = 'seed';
-    const handle: ExecutionHandle = ExecutionLifecycleService.registerExecution(
+    const handle: ExecutionHandle = ExecutionLifecycleService.attachExecution(
       4321,
       {
         executionMethod: 'child_process',
@@ -211,7 +211,7 @@ describe('ExecutionLifecycleService', () => {
   it('supports late subscription catch-up after backgrounding an external execution', async () => {
     let output = 'seed';
     const onExit = vi.fn();
-    const handle = ExecutionLifecycleService.registerExecution(4322, {
+    const handle = ExecutionLifecycleService.attachExecution(4322, {
       executionMethod: 'child_process',
       getBackgroundOutput: () => output,
       getSubscriptionSnapshot: () => output,
@@ -258,7 +258,7 @@ describe('ExecutionLifecycleService', () => {
   it('kills external executions and settles pending promises', async () => {
     const terminate = vi.fn();
     const onExit = vi.fn();
-    const handle = ExecutionLifecycleService.registerExecution(4323, {
+    const handle = ExecutionLifecycleService.attachExecution(4323, {
       executionMethod: 'child_process',
       initialOutput: 'running',
       kill: terminate,
@@ -276,14 +276,14 @@ describe('ExecutionLifecycleService', () => {
   });
 
   it('rejects duplicate execution registration for active execution IDs', () => {
-    ExecutionLifecycleService.registerExecution(4324, {
+    ExecutionLifecycleService.attachExecution(4324, {
       executionMethod: 'child_process',
     });
 
     expect(() => {
-      ExecutionLifecycleService.registerExecution(4324, {
+      ExecutionLifecycleService.attachExecution(4324, {
         executionMethod: 'child_process',
       });
-    }).toThrow('Execution 4324 is already registered.');
+    }).toThrow('Execution 4324 is already attached.');
   });
 });

packages/core/src/services/executionLifecycleService.ts

@@ -167,12 +167,12 @@ export class ExecutionLifecycleService {
     this.nextExecutionId = NON_PROCESS_EXECUTION_ID_START;
   }
 
-  static registerExecution(
+  static attachExecution(
     executionId: number,
     registration: ExternalExecutionRegistration,
   ): ExecutionHandle {
     if (this.activeExecutions.has(executionId) || this.activeResolvers.has(executionId)) {
-      throw new Error(`Execution ${executionId} is already registered.`);
+      throw new Error(`Execution ${executionId} is already attached.`);
     }
     this.exitedExecutionInfo.delete(executionId);
 

packages/core/src/services/shellExecutionService.ts

@@ -258,7 +258,7 @@ export class ShellExecutionService {
       };
 
       const lifecycleHandle = child.pid
-        ? ExecutionLifecycleService.registerExecution(child.pid, {
+        ? ExecutionLifecycleService.attachExecution(child.pid, {
             executionMethod: 'child_process',
             getBackgroundOutput: () => state.output,
             getSubscriptionSnapshot: () => state.output || undefined,
@@ -554,7 +554,7 @@ export class ShellExecutionService {
         maxSerializedLines: shellExecutionConfig.maxSerializedLines,
       });
 
-      const result = ExecutionLifecycleService.registerExecution(ptyPid, {
+      const result = ExecutionLifecycleService.attachExecution(ptyPid, {
         executionMethod: ptyInfo?.name ?? 'node-pty',
         writeInput: (input) => {
           if (!ExecutionLifecycleService.isActive(ptyPid)) {