claude-code: load MCP config via plugin dir

Claude Code rejects `--mcp-config` once the Home Manager wrapper injects
it around subcommands, which breaks commands like `claude mcp list`.
Claude Code 2.1.76 fixed `--plugin-dir` so it no longer consumes
following subcommands, so use that path for the generated MCP config
instead.

Generate a plugin directory with a manifest and `.mcp.json`, wrap
`claude` with `--plugin-dir` before user arguments, and snapshot that
wrapper directly in the tests. Keep the existing LSP support in the
generated plugin directory as well, and add coverage for the combined
MCP+LSP case plus the MCP integration merge path.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

tests/modules/programs/claude-code/expected-lsp-plugin.json

@@ -0,0 +1,21 @@
+{
+  "go": {
+    "args": [
+      "serve"
+    ],
+    "command": "gopls",
+    "extensionToLanguage": {
+      ".go": "go"
+    }
+  },
+  "typescript": {
+    "args": [
+      "--stdio"
+    ],
+    "command": "typescript-language-server",
+    "extensionToLanguage": {
+      ".ts": "typescript",
+      ".tsx": "typescriptreact"
+    }
+  }
+}