refactor(config): Standardize env var access and config getters

This commit focuses on standardizing configuration and API key access patterns across key modules as part of subtask 61.34.

Key changes include:

- Refactored `ai-services.js` to remove global AI clients and use `resolveEnvVariable` for API key checks. Client instantiation now relies on `getAnthropicClient`/`getPerplexityClient` accepting a session object.

- Refactored `task-manager.js` (`analyzeTaskComplexity` function) to use the unified `generateTextService` from `ai-services-unified.js`, removing direct AI client calls.

- Replaced direct `process.env` access for model parameters and other configurations (`PERPLEXITY_MODEL`, `CONFIG.*`) in `task-manager.js` with calls to the appropriate getters from `config-manager.js` (e.g., `getResearchModelId(session)`, `getMainMaxTokens(session)`).

- Ensured `utils.js` (`resolveEnvVariable`) correctly handles potentially undefined session objects.

- Updated function signatures where necessary to propagate the `session` object for correct context-aware configuration/key retrieval.

This moves towards the goal of using `ai-client-factory.js` and `ai-services-unified.js` as the standard pattern for AI interactions and centralizing configuration management through `config-manager.js`.

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

@@ -0,0 +1,30 @@
+/**
+ * Checks if a task with the given ID exists
+ * @param {Array} tasks - Array of tasks to search
+ * @param {string|number} taskId - ID of task or subtask to check
+ * @returns {boolean} Whether the task exists
+ */
+function taskExists(tasks, taskId) {
+	// Handle subtask IDs (e.g., "1.2")
+	if (typeof taskId === 'string' && taskId.includes('.')) {
+		const [parentIdStr, subtaskIdStr] = taskId.split('.');
+		const parentId = parseInt(parentIdStr, 10);
+		const subtaskId = parseInt(subtaskIdStr, 10);
+
+		// Find the parent task
+		const parentTask = tasks.find((t) => t.id === parentId);
+
+		// If parent exists, check if subtask exists
+		return (
+			parentTask &&
+			parentTask.subtasks &&
+			parentTask.subtasks.some((st) => st.id === subtaskId)
+		);
+	}
+
+	// Handle regular task IDs
+	const id = parseInt(taskId, 10);
+	return tasks.some((t) => t.id === id);
+}
+
+export default taskExists;