feat(mcp): add streamable HTTP and stdio (#1911)

* feat(mcp): add streamable HTTP

alongside with frontend UI change, w/ support for stdio

* fix(mcp): address copilot reviews

* Update src/langbot/pkg/provider/tools/loaders/mcp.py

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix: resolve copilot reviews

* fix: Message -> MessageChunk

* feat: upgrade mcp module

* feat: add i18n

* feat(mcp): enhance MCPCardComponent with mode badge and reorder select items in MCPFormDialog

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: WangCham <651122857@qq.com>
Co-authored-by: Junyan Qin (Chin) <rockchinq@gmail.com>

web/src/i18n/locales/en-US.ts

@@ -467,8 +467,10 @@ const enUS = {
     getServerListError: 'Failed to get MCP server list: ',
     serverName: 'Server Name',
     serverMode: 'Connection Mode',
+    selectMode: 'Select Mode',
     stdio: 'Stdio Mode',
     sse: 'SSE Mode',
+    http: 'HTTP Mode',
     noServerInstalled: 'No MCP servers configured',
     serverNameRequired: 'Server name cannot be empty',
     commandRequired: 'Command cannot be empty',