Add external MCP server support (stdio JSON-RPC)

Lets the AI connect to any external stdio MCP server (e.g. safaridriver
--mcp) configured in Settings, with tools auto-discovered and prefixed
by server slug. Includes crash detection with backoff restart (5s/15s/30s)
and a Settings UI to add/enable/disable/remove servers.

Fixes the temp-dir allowlist in MCPService.isPathAllowed to also match
/tmp and /private/tmp (not just NSTemporaryDirectory(), which resolves
to a different per-user Darwin temp dir) so the MCP file tools can
actually read files external servers and image generation write there.
Also switches the Add Server sheet's argument parsing to a quote-aware
tokenizer so args containing spaces survive intact.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

oAI/Services/MCPService.swift

@@ -98,6 +98,17 @@ class MCPService {
 
     func isPathAllowed(_ path: String) -> Bool {
         let resolved = ((path as NSString).expandingTildeInPath as NSString).standardizingPath
+        // Always allow the system temp directory — external MCP servers and tools write
+        // intermediate data there (e.g. Safari MCP page-content files, generated images).
+        // Check both NSTemporaryDirectory() (per-user Darwin temp dir) and /tmp (what this
+        // codebase's own temp files actually use, e.g. ChatViewModel's /tmp/oai_generated_*
+        // and ExternalMCPClient's /tmp/oai_mcp_* — they resolve to different directories.
+        let tmpCandidates = [
+            (NSTemporaryDirectory() as NSString).standardizingPath,
+            "/tmp",
+            "/private/tmp"
+        ]
+        if tmpCandidates.contains(where: { resolved.hasPrefix($0) }) { return true }
         return allowedFolders.contains { resolved.hasPrefix($0) }
     }
 
@@ -310,6 +321,9 @@ class MCPService {
             ))
         }
 
+        // Add tools from external MCP servers (stdio JSON-RPC protocol)
+        tools.append(contentsOf: ExternalMCPManager.shared.getToolSchemas())
+
         return tools
     }
 
@@ -472,6 +486,10 @@ class MCPService {
             return await executePersonalDataAction(toolName: name, argumentsJSON: arguments, summary: summary)
 
         default:
+            // Route to external MCP servers (stdio JSON-RPC)
+            if ExternalMCPManager.shared.isExternalTool(name) {
+                return await ExternalMCPManager.shared.executeTool(name: name, argumentsJSON: arguments)
+            }
             // Route anytype_* tools to AnytypeMCPService
             if name.hasPrefix("anytype_") {
                 return await anytypeService.executeTool(name: name, arguments: arguments)