release(v0.2.0): streaming, MCP protocol, Browser Hand, security enhancements

## Major Features

### Streaming Response System
- Implement LlmDriver trait with `stream()` method returning async Stream
- Add SSE parsing for Anthropic and OpenAI API streaming
- Integrate Tauri event system for frontend streaming (`stream:chunk` events)
- Add StreamChunk types: Delta, ToolStart, ToolEnd, Complete, Error

### MCP Protocol Implementation
- Add MCP JSON-RPC 2.0 types (mcp_types.rs)
- Implement stdio-based MCP transport (mcp_transport.rs)
- Support tool discovery, execution, and resource operations

### Browser Hand Implementation
- Complete browser automation with Playwright-style actions
- Support Navigate, Click, Type, Scrape, Screenshot, Wait actions
- Add educational Hands: Whiteboard, Slideshow, Speech, Quiz

### Security Enhancements
- Implement command whitelist/blacklist for shell_exec tool
- Add SSRF protection with private IP blocking
- Create security.toml configuration file

## Test Improvements
- Fix test import paths (security-utils, setup)
- Fix vi.mock hoisting issues with vi.hoisted()
- Update test expectations for validateUrl and sanitizeFilename
- Add getUnsupportedLocalGatewayStatus mock

## Documentation Updates
- Update architecture documentation
- Improve configuration reference
- Add quick-start guide updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

desktop/src/components/IdentityChangeProposal.tsx

@@ -331,7 +331,8 @@ export function IdentityChangeProposalPanel() {
       setSnapshots(agentSnapshots);
     } catch (err) {
       console.error('[IdentityChangeProposal] Failed to approve:', err);
-      setError('审批失败');
+      const message = err instanceof Error ? err.message : '审批失败，请重试';
+      setError(`审批失败: ${message}`);
     } finally {
       setProcessingId(null);
     }
@@ -348,7 +349,8 @@ export function IdentityChangeProposalPanel() {
       setProposals(pendingProposals);
     } catch (err) {
       console.error('[IdentityChangeProposal] Failed to reject:', err);
-      setError('拒绝失败');
+      const message = err instanceof Error ? err.message : '拒绝失败，请重试';
+      setError(`拒绝失败: ${message}`);
     } finally {
       setProcessingId(null);
     }
@@ -365,7 +367,8 @@ export function IdentityChangeProposalPanel() {
       setSnapshots(agentSnapshots);
     } catch (err) {
       console.error('[IdentityChangeProposal] Failed to restore:', err);
-      setError('恢复失败');
+      const message = err instanceof Error ? err.message : '恢复失败，请重试';
+      setError(`恢复失败: ${message}`);
     } finally {
       setProcessingId(null);
     }