fix(ci): update MSRV to 1.88 and fix Windows VFS path handling

- Update rust-version from 1.85 to 1.88 to match Wasmtime 38.0 requirements
- Fix VFS builder path joining to maintain Unix-style paths on all platforms
- Refactor collapsible_if in config validation per new clippy lint

Fixes:
- MSRV check failure: Wasmtime 38.0 requires Rust 1.88.0
- Windows test failures: VFS path separator handling on Windows
  - test_complete_generation_workflow_vkteams
  - test_empty_server_generation
  - test_complex_schema_generation
  - test_vfs_directory_listing

All 314 tests now pass on all platforms.

Author: bug-ops

Cargo.toml

@@ -15,7 +15,7 @@ resolver = "2"
 [workspace.package]
 version = "0.1.0"
 edition = "2024"
-rust-version = "1.85"
+rust-version = "1.88"
 authors = ["MCP Execution Team"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/bug-ops/mcp-execution"

crates/mcp-core/src/config.rs

@@ -180,10 +180,10 @@ impl RuntimeConfig {
             return Err("Execution timeout must be greater than zero".to_string());
         }
 
-        if let Some(cache_dir) = &self.cache_dir {
-            if cache_dir.as_os_str().is_empty() {
-                return Err("Cache directory path cannot be empty".to_string());
-            }
+        if let Some(cache_dir) = &self.cache_dir
+            && cache_dir.as_os_str().is_empty()
+        {
+            return Err("Cache directory path cannot be empty".to_string());
         }
 
         Ok(())

crates/mcp-vfs/src/builder.rs

@@ -117,12 +117,20 @@ impl VfsBuilder {
     #[must_use]
     pub fn from_generated_code(code: GeneratedCode, base_path: impl AsRef<Path>) -> Self {
         let mut builder = Self::new();
-        let base = base_path.as_ref();
+        let base = base_path.as_ref().to_string_lossy();
+
+        // Ensure base path ends with a trailing slash for proper joining
+        let base_normalized = if base.ends_with('/') {
+            base.into_owned()
+        } else {
+            format!("{}/", base)
+        };
 
         for file in code.files {
-            // Construct full path by joining base path with file path
-            let full_path = base.join(&file.path);
-            builder = builder.add_file(full_path, file.content);
+            // Use string concatenation to maintain Unix-style paths on all platforms
+            // This ensures VFS paths are always forward-slash separated, even on Windows
+            let full_path = format!("{}{}", base_normalized, file.path);
+            builder = builder.add_file(full_path.as_str(), file.content);
         }
 
         builder