feat(telemetry): Integrate AI usage telemetry into update-subtask

This commit applies the standard telemetry pattern to the update-subtask command and its corresponding MCP tool.

Key Changes:

1.  Core Logic (scripts/modules/task-manager/update-subtask-by-id.js):
    -   The call to generateTextService now includes commandName: 'update-subtask' and outputType.
    -   The full response { mainResult, telemetryData } is captured.
    -   mainResult (the AI-generated text) is used for the appended content.
    -   If running in CLI mode (outputFormat === 'text'), displayAiUsageSummary is called with the telemetryData.
    -   The function now returns { updatedSubtask: ..., telemetryData: ... }.

2.  Direct Function (mcp-server/src/core/direct-functions/update-subtask-by-id.js):
    -   The call to the core updateSubtaskById function now passes the necessary context for telemetry (commandName, outputType).
    -   The successful response object now correctly extracts coreResult.telemetryData and includes it in the data.telemetryData field returned to the MCP client.

mcp-server/src/core/direct-functions/update-subtask-by-id.js

@@ -108,18 +108,24 @@ export async function updateSubtaskByIdDirect(args, log, context = {}) {
 
 		try {
 			// Execute core updateSubtaskById function
-			const updatedSubtask = await updateSubtaskById(
+			const coreResult = await updateSubtaskById(
 				tasksPath,
 				subtaskIdStr,
 				prompt,
 				useResearch,
-				{ mcpLog: logWrapper, session, projectRoot },
+				{
+					mcpLog: logWrapper,
+					session,
+					projectRoot,
+					commandName: 'update-subtask',
+					outputType: 'mcp'
+				},
 				'json'
 			);
 
-			if (updatedSubtask === null) {
+			if (!coreResult || coreResult.updatedSubtask === null) {
 				const message = `Subtask ${id} or its parent task not found.`;
-				logWrapper.error(message); // Log as error since it couldn't be found
+				logWrapper.error(message);
 				return {
 					success: false,
 					error: { code: 'SUBTASK_NOT_FOUND', message: message },
@@ -136,9 +142,10 @@ export async function updateSubtaskByIdDirect(args, log, context = {}) {
 					message: `Successfully updated subtask with ID ${subtaskIdStr}`,
 					subtaskId: subtaskIdStr,
 					parentId: subtaskIdStr.split('.')[0],
-					subtask: updatedSubtask,
+					subtask: coreResult.updatedSubtask,
 					tasksPath,
-					useResearch
+					useResearch,
+					telemetryData: coreResult.telemetryData
 				},
 				fromCache: false
 			};