fix: clarify MCP slash command labels (warpdotdev#9887)

Closes warpdotdev#9880

## Summary
- Clarified `/add-mcp` so the slash-command menu says it adds a server
via the MCP settings page.
- Renamed the bundled file-config MCP skill display name to
`agent-add-mcp` while keeping its existing description.
- Added regression tests for both updated labels.

## Validation
- `cargo fmt`
- `git --no-pager diff --check`
- `cargo test -p ai test_parse_with_front_matter`
- Lightweight direct metadata check for `/add-mcp` and bundled
`agent-add-mcp` strings

Validation limitations:
- `cargo test -p warp add_mcp --lib` was attempted twice, including with
`CARGO_BUILD_JOBS=1`, but the sandbox killed the app crate compile with
SIGKILL.
- `CARGO_BUILD_JOBS=1 cargo clippy --workspace --all-targets
--all-features --tests -- -D warnings` was attempted. After installing
missing `libclang`, it remained blocked because the sandbox cannot
access the private `warp-channel-config` repository needed to generate
release-bundle channel config files for all-features clippy.

## Notes
- The implementation is intentionally scoped to the requested minimal
UI/text disambiguation.

---------

Co-authored-by: Oz <oz-agent@warp.dev>
Co-authored-by: Varoon Kodithala <116049637+vkodithala@users.noreply.github.com>
Co-authored-by: vkodithala <varoon@warp.dev>

Author: 3 people

app/src/search/slash_command_menu/static_commands/commands.rs

@@ -29,7 +29,7 @@ pub static CLOUD_AGENT: LazyLock<StaticCommand> = LazyLock::new(|| StaticCommand
 
 pub const ADD_MCP: StaticCommand = StaticCommand {
     name: "/add-mcp",
-    description: "Add new MCP server",
+    description: "Add a new MCP server via the MCP settings page",
     icon_path: "bundled/svg/dataflow.svg",
     availability: Availability::AI_ENABLED,
     auto_enter_ai_mode: false,

resources/bundled/skills/add-mcp-server/SKILL.md

@@ -1,5 +1,5 @@
 ---
-name: add-mcp-server
+name: agent-add-mcp
 description: Use this skill when helping users add MCP servers to their Warp configuration.
 ---