fix(mcp): always register self.assets.set_download_url tool for 32MB flash devices (#1971)

* fix(m5stack-tab5): remove stale esp_video==0.7.0 dependency instructions

The README previously instructed users to override esp_video to 0.7.0
and esp_ipa to 0.1.0, but this causes build failures because:
- esp_video 0.7.0 does not export esp_video_deinit(), resulting in
  linker errors ('MAP_FAILED' and 'esp_video_deinit' not declared)
- The project's main/idf_component.yml already pins the correct
  version (esp_video==1.3.1) that the source code expects

Users should now use the default dependency versions from idf_component.yml
without modification.

Fixes #1957

* fix(mcp): always register self.assets.set_download_url tool

On 32MB flash devices the assets partition layout differs from the
default, causing partition_valid() to return false and silently
skipping registration of the self.assets.set_download_url MCP tool.
Users see 'Unknown tool: self.assets.set_download_url' from their MCP
client.

The tool writes to Settings storage which works regardless of the
partition map, so the partition_valid() guard is unnecessary.
Move the AddUserOnlyTool call outside the guard so the tool is always
available for explicit configuration via MCP.

Fixes #1962

---------

Co-authored-by: Aayush Pratap Singh <aayushpratap.singh@gmail.com>

main/mcp_server.cc

@@ -284,10 +284,8 @@ void McpServer::AddUserOnlyTools() {
     }
 #endif // HAVE_LVGL
 
-    // Assets download url
-    auto& assets = Assets::GetInstance();
-    if (assets.partition_valid()) {
-        AddUserOnlyTool("self.assets.set_download_url", "Set the download url for the assets",
+    // Assets download url (always registered — Settings storage works regardless of partition layout)
+    AddUserOnlyTool("self.assets.set_download_url", "Set the download url for the assets",
             PropertyList({
                 Property("url", kPropertyTypeString)
             }),