fix: Correct TTY check for AI progress indicator in CLI

Addresses `process.stdout.clearLine is not a function` error when running AI-dependent commands non-interactively (e.g., `update-subtask`).

Adds `process.stdout.isTTY` check before attempting to use terminal-specific output manipulations.

feat: Implement initial config manager for AI models

Adds `scripts/modules/config-manager.js` to handle reading/writing model selections from/to `.taskmasterconfig`.

Implements core functions: findProjectRoot, read/writeConfig, validateModel, get/setModel.

Defines valid model lists. Completes initial work for Subtask 61.1.

package.json

@@ -39,6 +39,7 @@
 	"license": "MIT WITH Commons-Clause",
 	"dependencies": {
 		"@anthropic-ai/sdk": "^0.39.0",
+		"ai": "^4.3.6",
 		"boxen": "^8.0.1",
 		"chalk": "^4.1.2",
 		"cli-table3": "^0.6.5",