fix: use path.join for cross-platform test compatibility

The extension uses path.relative() which returns OS-native separators.
On Windows this produces backslashes (src\sample.ts) while the tests
were hardcoding forward slashes (src/sample.ts), causing path comparison
failures in CI.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: fegge

test/extension/suite/commands.test.ts

@@ -213,7 +213,8 @@ suite("Command Execution", () => {
 
         // First, mark a file as audited to ensure there's content in the day log
         await openTestFile();
-        const relativePath = "src/sample.ts";
+        // Use path.join for cross-platform compatibility (Windows uses backslashes)
+        const relativePath = path.join("src", "sample.ts");
 
         // Check if file is already audited
         const dataBefore = readWeauditData(workspaceFolder);

test/extension/suite/decorations.test.ts

@@ -87,7 +87,8 @@ suite("Editor Decorations", () => {
         this.timeout(10000);
 
         await openTestFile();
-        const relativePath = "src/sample.ts";
+        // Use path.join for cross-platform compatibility (Windows uses backslashes)
+        const relativePath = path.join("src", "sample.ts");
 
         // Get the initial state
         const dataBefore = readWeauditData(workspaceFolder);
@@ -110,7 +111,8 @@ suite("Editor Decorations", () => {
         this.timeout(10000);
 
         const editor = await openTestFile();
-        const relativePath = "src/sample.ts";
+        // Use path.join for cross-platform compatibility (Windows uses backslashes)
+        const relativePath = path.join("src", "sample.ts");
 
         // Ensure the file is not fully audited (which would prevent partial auditing)
         // The previous test may have marked it as fully audited