fix(codex): strip synced [mcp_servers] from provider snapshots on backfill

MCP servers are owned by the DB mcp_servers table; the [mcp_servers]
section in live config.toml is only a projection re-synced after every
live write. When switching away baked that projection into the stored
provider snapshot, servers deleted in the app were resurrected the next
time that provider was activated -- per-entry reconcile only knows rows
that still exist in the DB, so it can never clean up such orphans.

Strip [mcp_servers] (and the legacy [mcp.servers] form) from the live
settings during switch-away backfill. Previously polluted snapshots
self-heal the next time the user switches away from them.

src-tauri/src/codex_config.rs

@@ -1473,6 +1473,45 @@ pub fn strip_codex_unified_session_bucket_from_settings(
     Ok(())
 }
 
+/// Backfill helper: strip `[mcp_servers]` from a live `{ auth, config }`
+/// settings object before it is stored back to the DB.
+///
+/// MCP 服务器的 SSOT 是 DB 的 mcp_servers 表，live `config.toml` 里的
+/// `[mcp_servers]` 只是每次写 live 之后由 MCP 同步重新投影的产物。若回填时
+/// 烙进供应商存储配置，已在应用里删除的服务器会随下次激活该供应商被写回
+/// live，而逐条 reconcile 只认识 DB 现存条目、永远清不掉这种孤儿。
+pub fn strip_codex_mcp_servers_from_settings(settings: &mut Value) -> Result<(), AppError> {
+    let Some(config_text) = settings
+        .get("config")
+        .and_then(|value| value.as_str())
+        .map(str::to_string)
+    else {
+        return Ok(());
+    };
+    if !config_text.contains("mcp") {
+        return Ok(());
+    }
+    let mut doc = config_text
+        .parse::<DocumentMut>()
+        .map_err(|e| AppError::Message(format!("Invalid Codex config.toml: {e}")))?;
+    let mut changed = doc.as_table_mut().remove("mcp_servers").is_some();
+    // 历史错误格式 [mcp.servers] 一并清理（live 侧 MCP 同步也做同样迁移）
+    if let Some(mcp_tbl) = doc.get_mut("mcp").and_then(|item| item.as_table_like_mut()) {
+        if mcp_tbl.remove("servers").is_some() {
+            changed = true;
+        }
+        if mcp_tbl.is_empty() {
+            doc.as_table_mut().remove("mcp");
+        }
+    }
+    if changed {
+        if let Some(obj) = settings.as_object_mut() {
+            obj.insert("config".to_string(), Value::String(doc.to_string()));
+        }
+    }
+    Ok(())
+}
+
 /// Route a Codex live write between full auth+config or config-only.
 ///
 /// Official providers with usable login material own `auth.json`. Third-party
@@ -1803,6 +1842,41 @@ requires_openai_auth = true
         assert!(settings.pointer("/auth/tokens/access_token").is_some());
     }
 
+    #[test]
+    fn strip_mcp_servers_from_settings_removes_table_and_legacy_form() {
+        let mut settings = json!({
+            "auth": { "OPENAI_API_KEY": "sk-test" },
+            "config": "# user comment\nmodel = \"gpt-5.5\"\n\n[mcp_servers.echo]\ntype = \"stdio\"\ncommand = \"echo\"\n\n[mcp.servers.legacy]\ncommand = \"noop\"\n",
+        });
+        strip_codex_mcp_servers_from_settings(&mut settings).expect("strip mcp");
+        let config = settings
+            .get("config")
+            .and_then(|v| v.as_str())
+            .expect("config text");
+        assert!(!config.contains("mcp_servers"), "got: {config}");
+        assert!(
+            !config.contains("[mcp"),
+            "legacy [mcp.servers] gone: {config}"
+        );
+        assert!(config.contains("# user comment"), "comments preserved");
+        assert!(config.contains("model = \"gpt-5.5\""));
+    }
+
+    #[test]
+    fn strip_mcp_servers_from_settings_is_noop_without_mcp() {
+        let original = "# comment\nmodel = \"gpt-5.5\"\n";
+        let mut settings = json!({
+            "auth": {},
+            "config": original,
+        });
+        strip_codex_mcp_servers_from_settings(&mut settings).expect("strip mcp");
+        assert_eq!(
+            settings.get("config").and_then(|v| v.as_str()),
+            Some(original),
+            "config text must be byte-identical when nothing is stripped"
+        );
+    }
+
     #[test]
     fn extract_base_url_prefers_active_provider_section() {
         let input = r#"model_provider = "azure"