fix: enforce sequential subtask ID numbering in AI prompts

Fixed issue where AI was generating inconsistent subtask IDs (101-105, 601-603)
instead of sequential numbering (1, 2, 3...) after the generateObject migration.

Changes:
- Updated all expand-task prompt variants with forceful "CRITICAL" instructions
- Made ID requirements explicit with examples: id={{nextSubtaskId}}, id={{nextSubtaskId}}+1
- Added warning not to use parent task ID in subtask numbering
- Removed parseSubtasksFromText post-processing that was overwriting AI-generated IDs

This ensures subtasks display correctly as X.1, X.2, X.3 format and the
`tm show X.Y` command works as expected.

scripts/modules/task-manager/expand-task.js

@@ -199,6 +199,10 @@ async function expandTask(
 		}
 
 		// Determine prompt content AND system prompt
+		// Calculate the next subtask ID to match current behavior:
+		// - Start from the number of existing subtasks + 1
+		// - This creates sequential IDs: 1, 2, 3, 4...
+		// - Display format shows as parentTaskId.subtaskId (e.g., "1.1", "1.2", "2.1")
 		const nextSubtaskId = (task.subtasks?.length || 0) + 1;
 
 		// Load prompts using PromptManager
@@ -259,7 +263,6 @@ async function expandTask(
 			hasCodebaseAnalysis: hasCodebaseAnalysisCapability,
 			projectRoot: projectRoot || ''
 		};
-
 		let variantKey = 'default';
 		if (expansionPromptText) {
 			variantKey = 'complexity-report';