fix: resolve OpenAI Compatible settings persistence issues

- Fixed storage mismatch in config-manager.ts where settings were read from incorrect top-level keys instead of nested codebaseIndexConfig object
- Updated CodebaseIndexConfig type definition to include OpenAI Compatible fields
- Removed complex workaround logic from import/export that is no longer needed
- Fixed UI bug in CodeIndexPopover where saved settings were not displayed
- Updated unit tests to match the corrected architecture

This addresses Dan's review feedback about the root cause of the bug and ensures OpenAI Compatible provider settings are properly saved, displayed, and exported.

Author: MuriloFP

webview-ui/src/components/chat/CodeIndexPopover.tsx

@@ -117,9 +117,10 @@ export const CodeIndexPopover: React.FC<CodeIndexPopoverProps> = ({
 					codebaseIndexConfig.codebaseIndexSearchMaxResults || CODEBASE_INDEX_DEFAULTS.DEFAULT_SEARCH_RESULTS,
 				codeIndexOpenAiKey: "",
 				codeIndexQdrantApiKey: "",
-				codebaseIndexOpenAiCompatibleBaseUrl: "",
+				codebaseIndexOpenAiCompatibleBaseUrl: codebaseIndexConfig.codebaseIndexOpenAiCompatibleBaseUrl || "",
 				codebaseIndexOpenAiCompatibleApiKey: "",
-				codebaseIndexOpenAiCompatibleModelDimension: undefined,
+				codebaseIndexOpenAiCompatibleModelDimension:
+					codebaseIndexConfig.codebaseIndexOpenAiCompatibleModelDimension || undefined,
 				codebaseIndexGeminiApiKey: "",
 			}
 			setInitialSettings(settings)