Fix/MCP exposure v2 TODO's (#675)

* fix: OAuth tokens secure storage for Windows & Linux

* fix(mcp): MCP Tool Re-exposure & Strict Input Validation

Fixes the MCP re-exposure bug by correctly handling tool deduplication, input validation with Ajv, and structured output (including images). Also disables experimental API betas by default to prevent 500 errors on external accounts.

* fix(mcp): skip official registry prefetch in non-first-party mode

Prevents unnecessary calls to Anthropic's MCP registry when using other API providers.

* fix(cli): disable experimental API betas by default

This prevents 500 errors from Anthropic's API when tool-calling with non-Anthropic accounts or models that don't support certain beta features.

* fix: issues raised in the PR review for #675

src/cli/handlers/mcp.tsx

@@ -11,7 +11,12 @@ import { MCPServerDesktopImportDialog } from '../../components/MCPServerDesktopI
 import { render } from '../../ink.js';
 import { KeybindingSetup } from '../../keybindings/KeybindingProviderSetup.js';
 import { type AnalyticsMetadata_I_VERIFIED_THIS_IS_NOT_CODE_OR_FILEPATHS, logEvent } from '../../services/analytics/index.js';
-import { clearMcpClientConfig, clearServerTokensFromLocalStorage, readClientSecret, saveMcpClientSecret } from '../../services/mcp/auth.js';
+import {
+  clearMcpClientConfig,
+  clearServerTokensFromSecureStorage,
+  readClientSecret,
+  saveMcpClientSecret,
+} from '../../services/mcp/auth.js'
 import { doctorAllServers, doctorServer, type McpDoctorReport, type McpDoctorScopeFilter } from '../../services/mcp/doctor.js';
 import { connectToServer, getMcpServerConnectionBatchSize } from '../../services/mcp/client.js';
 import { addMcpConfig, getAllMcpConfigs, getMcpConfigByName, getMcpConfigsByScope, removeMcpConfig } from '../../services/mcp/config.js';