feat: add Claude Code provider support

Implements Claude Code as a new AI provider that uses the Claude Code CLI
without requiring API keys. This enables users to leverage Claude models
through their local Claude Code installation.

Key changes:
- Add complete AI SDK v1 implementation for Claude Code provider
  - Custom SDK with streaming/non-streaming support
  - Session management for conversation continuity
  - JSON extraction for object generation mode
  - Support for advanced settings (maxTurns, allowedTools, etc.)

- Integrate Claude Code into Task Master's provider system
  - Update ai-services-unified.js to handle keyless authentication
  - Add provider to supported-models.json with opus/sonnet models
  - Ensure correct maxTokens values are applied (opus: 32000, sonnet: 64000)

- Fix maxTokens configuration issue
  - Add max_tokens property to getAvailableModels() output
  - Update setModel() to properly handle claude-code models
  - Create update-config-tokens.js utility for init process

- Add comprehensive documentation
  - User guide with configuration examples
  - Advanced settings explanation and future integration options

The implementation maintains full backward compatibility with existing
providers while adding seamless Claude Code support to all Task Master
commands.

scripts/modules/config-manager.js

@@ -507,6 +507,11 @@ function isApiKeySet(providerName, session = null, projectRoot = null) {
 		return true; // Indicate key status is effectively "OK"
 	}
 
+	// Claude Code doesn't require an API key
+	if (providerName?.toLowerCase() === 'claude-code') {
+		return true; // No API key needed
+	}
+
 	const keyMap = {
 		openai: 'OPENAI_API_KEY',
 		anthropic: 'ANTHROPIC_API_KEY',
@@ -517,6 +522,7 @@ function isApiKeySet(providerName, session = null, projectRoot = null) {
 		openrouter: 'OPENROUTER_API_KEY',
 		xai: 'XAI_API_KEY',
 		vertex: 'GOOGLE_API_KEY', // Vertex uses the same key as Google
+		'claude-code': 'CLAUDE_CODE_API_KEY', // Not actually used, but included for consistency
 		bedrock: 'AWS_ACCESS_KEY_ID' // Bedrock uses AWS credentials
 		// Add other providers as needed
 	};
@@ -601,6 +607,8 @@ function getMcpApiKeyStatus(providerName, projectRoot = null) {
 				break;
 			case 'ollama':
 				return true; // No key needed
+			case 'claude-code':
+				return true; // No key needed
 			case 'mistral':
 				apiKeyToCheck = mcpEnv.MISTRAL_API_KEY;
 				placeholderValue = 'YOUR_MISTRAL_API_KEY_HERE';
@@ -664,7 +672,8 @@ function getAvailableModels() {
 					provider: provider,
 					swe_score: sweScore,
 					cost_per_1m_tokens: cost,
-					allowed_roles: allowedRoles
+					allowed_roles: allowedRoles,
+					max_tokens: modelObj.max_tokens
 				});
 			});
 		} else {