fix: fix mcp-config validation error

[KenKinCOM]

Changed --mcp-config from {} to {"mcpServers":{}} to comply with newer Claude CLI versions that validate the mcpServers field presence.

This fixes the error: 'Invalid MCP configuration: mcpServers: Invalid input: expected record, received undefined'

[chuenchen309]

This one looks like it's already resolved on main. src-tauri/src/commands/claude_cli.rs now defines the empty isolated config as a named constant and uses it for --mcp-config:

const ISOLATED_MCP_CONFIG: &str = "{\"mcpServers\":{}}";

build_claude_cli_args passes ISOLATED_MCP_CONFIG (with a comment noting the required top-level mcpServers key), and the unit test asserts against it too. That's the same {} → {"mcpServers":{}} fix nashsu mentioned when closing #430 as fixed in v0.5.3, and it covers the --strict-mcp-config isolation path this PR targets.

So this change — and the byte-identical #440 and the named-constant version #465 — are now no-ops against main and can probably be closed. Just flagging the overlap so they don't need separate reviews.

[KenKinCOM]

谢谢你，我收到了.