fix: make Codex TOML base_url editing section-aware

Rewrite setCodexBaseUrl/extractCodexBaseUrl to understand TOML section
boundaries, ensuring base_url is written into the correct
[model_providers.<name>] section instead of being appended to file end.

- Add section-aware TOML helpers in providerConfigUtils.ts
- Extract shared update_codex_toml_field/remove_codex_toml_base_url_if
  in codex_config.rs, deduplicate proxy.rs TOML editing logic
- Replace scattered inline base_url regexes with extractCodexBaseUrl()
- Add comprehensive tests for both Rust and TypeScript implementations

src/components/providers/forms/hooks/useSpeedTestEndpoints.ts

@@ -3,6 +3,7 @@ import type { AppId } from "@/lib/api";
 import type { ProviderPreset } from "@/config/claudeProviderPresets";
 import type { CodexProviderPreset } from "@/config/codexProviderPresets";
 import type { ProviderMeta, EndpointCandidate } from "@/types";
+import { extractCodexBaseUrl } from "@/utils/providerConfigUtils";
 
 type PresetEntry = {
   id: string;
@@ -128,10 +129,9 @@ export function useSpeedTestEndpoints({
         }
       | undefined;
     const configStr = initialCodexConfig?.config ?? "";
-    // 从 TOML 中提取 base_url
-    const match = /base_url\s*=\s*["']([^"']+)["']/i.exec(configStr);
-    if (match?.[1]) {
-      add(match[1]);
+    const extractedBaseUrl = extractCodexBaseUrl(configStr);
+    if (extractedBaseUrl) {
+      add(extractedBaseUrl);
     }
 
     // 3. 预设中的 endpointCandidates
@@ -141,11 +141,9 @@ export function useSpeedTestEndpoints({
         const preset = entry.preset as CodexProviderPreset;
         // 添加预设自己的 baseUrl
         const presetConfig = preset.config || "";
-        const presetMatch = /base_url\s*=\s*["']([^"']+)["']/i.exec(
-          presetConfig,
-        );
-        if (presetMatch?.[1]) {
-          add(presetMatch[1]);
+        const presetBaseUrl = extractCodexBaseUrl(presetConfig);
+        if (presetBaseUrl) {
+          add(presetBaseUrl);
         }
         // 添加预设的候选端点
         if (preset.endpointCandidates) {