fix(market): allow installing remote (sse/streamable) servers from the market

[kwenhwang]

Summary

The market Install button runs isCommandAvailable(serverConfig['command']) for every entry. For remote servers (type: sse / type: streamable) the command field holds a URL, so this becomes which https://… (or where … on Windows), which can never succeed. The user gets the "command not found" dialog before the edit dialog opens — even though:

• _showEditDialog already handles sse/streamable entries (isRemote / isValidUrl checks at the save step), and
• loadMarketServers deliberately keeps entries whose command starts with http on mobile, where Process.run('which', …) cannot work at all.

So today no remote entry in mcp_server_market.json can be installed from the market on any platform; it has to be re-typed by hand via "+".

Change

lib/page/setting/mcp_server.dart — skip the PATH check when the entry is remote (type is sse/streamable, or command starts with http). Stdio entries are unchanged.

Validation

• Read-through of the install path (_buildServerCard → isCommandAvailable in lib/utils/process.dart → _showEditDialog) and of the remote-entry paths that already exist (initializeMcpServer type switch, loadMarketServers mobile filter).
• Not compiled locally (no Flutter toolchain on this machine) — relying on CI build.yml / format.yml (page_width: 150; the longest added line is 104 chars).

Companion PR: chatmcpclient/mcp_server_market — the first remote (streamable) entry in the market, which is what surfaced this.