test: repair test suite after R1-R3 refactors and add Claude Code tests

The R1-R3 refactors removed the per-provider handle*Error methods,
consolidated validators into validateNumberInRange, renamed Gemini's
buildGenerationConfig to buildConfig, and split OpenWebUI's message
conversion and response formatting into openwebui-strategies.ts.
44 of 91 existing tests broke as a result.

Changes:

claude.test.ts (8 -> 13 passing)
- Switch error mapping tests from handleAnthropicError to the base
  normalizeError method.
- Update temperature error-message expectation to match the new
  validateNumberInRange wording.

openai.test.ts (16 -> 22 passing)
- Same handleOpenAIError -> normalizeError switch.
- Add a regression test for the 429+"quota" path that goes through
  mapProviderError instead of the base mapping.

gemini.test.ts (17 -> 27 passing)
- Update getInfo expectations to the new default model (gemini-2.5)
  and provider version 2.0.0.
- Switch to normalizeError.
- Rename buildGenerationConfig -> buildConfig (renamed during R2).
- Update formatCompletionResponse mocks: the @google/genai SDK
  exposes response.text as a getter rather than walking
  candidates[0].content.parts.

openwebui.test.ts (4 -> 19 passing)
- Drop tests for convertMessages / convertMessagesToPrompt /
  formatChatResponse / formatOllamaResponse / makeRequest: these
  moved into openwebui-strategies.ts and openwebui-http.ts during R3
  and warrant their own test files.
- Add error-mapping tests covering the new mapProviderError +
  providerErrorMessages plumbing.

claude-code.test.ts (new, 18 tests)
- Constructor accepts subscription mode (empty config).
- getInfo advertises subscriptionAuth + requiresLocalCli.
- mapProviderError catches ENOENT and "not logged in".
- errorForSdkAssistantError covers each documented SDK error code.
- buildPrompt handles single-turn pass-through, multi-system
  combination, multi-turn flattening with role labels, and rejects
  empty turn lists.

Full suite: 100 pass / 0 fail across 5 files.

tests/openai.test.ts

@@ -73,7 +73,7 @@ describe('OpenAIProvider', () => {
           messages: [{ role: 'user', content: 'test' }],
           temperature: 1.5
         })
-      ).rejects.toThrow('Temperature must be a number between 0.0 and 1.0');
+      ).rejects.toThrow(/temperature must be at most 1/);
     });
 
     it('should validate top_p range', async () => {
@@ -85,7 +85,7 @@ describe('OpenAIProvider', () => {
           messages: [{ role: 'user', content: 'test' }],
           topP: 1.5
         })
-      ).rejects.toThrow('Top-p must be a number between 0.0 (exclusive) and 1.0 (inclusive)');
+      ).rejects.toThrow(/topP must be at most 1/);
     });
 
     it('should validate message format', async () => {
@@ -120,23 +120,25 @@ describe('OpenAIProvider', () => {
   });
 
   describe('error handling', () => {
+    const mapError = (err: any) => (provider as any).normalizeError(err);
+
     it('should handle authentication errors', () => {
       const error = new Error('Unauthorized');
       (error as any).status = 401;
-      
-      const providerError = (provider as any).handleOpenAIError(error);
-      
+
+      const providerError = mapError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.AUTHENTICATION);
-      expect(providerError.message).toContain('Authentication failed');
+      expect(providerError.message).toContain('OpenAI API key');
     });
 
     it('should handle rate limit errors', () => {
       const error = new Error('Rate limited');
       (error as any).status = 429;
-      
-      const providerError = (provider as any).handleOpenAIError(error);
-      
+
+      const providerError = mapError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.RATE_LIMIT);
       expect(providerError.message).toContain('Too many requests');
@@ -145,9 +147,9 @@ describe('OpenAIProvider', () => {
     it('should handle model not found errors', () => {
       const error = new Error('Model not found');
       (error as any).status = 404;
-      
-      const providerError = (provider as any).handleOpenAIError(error);
-      
+
+      const providerError = mapError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.MODEL_NOT_FOUND);
       expect(providerError.message).toContain('Model not found');
@@ -156,9 +158,9 @@ describe('OpenAIProvider', () => {
     it('should handle invalid request errors', () => {
       const error = new Error('Bad request');
       (error as any).status = 400;
-      
-      const providerError = (provider as any).handleOpenAIError(error);
-      
+
+      const providerError = mapError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.INVALID_REQUEST);
     });
@@ -166,21 +168,31 @@ describe('OpenAIProvider', () => {
     it('should handle server errors', () => {
       const error = new Error('Internal server error');
       (error as any).status = 500;
-      
-      const providerError = (provider as any).handleOpenAIError(error);
-      
+
+      const providerError = mapError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.NETWORK);
     });
 
     it('should handle unknown errors', () => {
       const error = new Error('Unknown error');
-      
-      const providerError = (provider as any).handleOpenAIError(error);
-      
+
+      const providerError = mapError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.UNKNOWN);
     });
+
+    it('should route 429 with quota to quota-specific message', () => {
+      const error = new Error('quota exceeded');
+      (error as any).status = 429;
+
+      const providerError = mapError(error);
+
+      expect(providerError.type).toBe(AIErrorType.RATE_LIMIT);
+      expect(providerError.message).toContain('Usage quota exceeded');
+    });
   });
 
   describe('message conversion', () => {