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/claude.test.ts

@@ -51,7 +51,7 @@ describe('ClaudeProvider', () => {
           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 message format', async () => {
@@ -78,19 +78,20 @@ describe('ClaudeProvider', () => {
     it('should handle authentication errors', () => {
       const error = new Error('Unauthorized');
       (error as any).status = 401;
-      
-      const providerError = (provider as any).handleAnthropicError(error);
-      
+
+      const providerError = (provider as any).normalizeError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.AUTHENTICATION);
+      expect(providerError.statusCode).toBe(401);
     });
 
     it('should handle rate limit errors', () => {
       const error = new Error('Rate limited');
       (error as any).status = 429;
-      
-      const providerError = (provider as any).handleAnthropicError(error);
-      
+
+      const providerError = (provider as any).normalizeError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.RATE_LIMIT);
     });
@@ -98,12 +99,22 @@ describe('ClaudeProvider', () => {
     it('should handle model not found errors', () => {
       const error = new Error('Model not found');
       (error as any).status = 404;
-      
-      const providerError = (provider as any).handleAnthropicError(error);
-      
+
+      const providerError = (provider as any).normalizeError(error);
+
       expect(providerError).toBeInstanceOf(AIProviderError);
       expect(providerError.type).toBe(AIErrorType.MODEL_NOT_FOUND);
     });
+
+    it('should route 400 with max_tokens to mapProviderError', () => {
+      const error = new Error('max_tokens too large');
+      (error as any).status = 400;
+
+      const providerError = (provider as any).normalizeError(error);
+
+      expect(providerError.type).toBe(AIErrorType.INVALID_REQUEST);
+      expect(providerError.message).toMatch(/Max tokens/);
+    });
   });
 
   describe('message conversion', () => {