Fix gitAdd to skip staging files ignored by .gitignore (#2707)

## Summary
- Add a pre-flight check in `gitAdd` to detect if a file is ignored by
`.gitignore` before attempting to stage it
- Skip staging ignored files gracefully with a debug log instead of
throwing an error
- This prevents errors when the AI attempts to stage files like
`.env.local` that should remain untracked

## Test plan
- [ ] Verify that staging a normal file still works correctly
- [ ] Create a `.gitignore` file that ignores a test file (e.g.,
`test.ignored`)
- [ ] Create the ignored file and attempt to stage it
- [ ] Confirm the file is skipped without error and a debug message is
logged

🤖 Generated with [Claude Code](https://claude.com/claude-code)
<!-- devin-review-badge-begin -->

---

<a href="https://app.devin.ai/review/dyad-sh/dyad/pull/2707"
target="_blank">
  <picture>
<source media="(prefers-color-scheme: dark)"
srcset="https://static.devin.ai/assets/gh-open-in-devin-review-dark.svg?v=1">
<img
src="https://static.devin.ai/assets/gh-open-in-devin-review-light.svg?v=1"
alt="Open with Devin">
  </picture>
</a>
<!-- devin-review-badge-end -->

---------

Co-authored-by: Will Chen <willchen90@gmail.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>

Author: 4 people

src/ipc/utils/git_utils.ts

@@ -419,6 +419,29 @@ export async function gitAddAll({ path }: GitBaseParams): Promise<void> {
 export async function gitAdd({ path, filepath }: GitFileParams): Promise<void> {
   const normalizedFilepath = normalizePath(filepath);
   const settings = readSettings();
+
+  // Check if the file is ignored by .gitignore before attempting to stage.
+  // This prevents errors when trying to stage files like .env.local.
+  // Skip the check when filepath is "." (stage-all), as "." is not a meaningful
+  // argument to git check-ignore and could incorrectly skip staging all files.
+  if (normalizedFilepath !== ".") {
+    let isIgnored = false;
+    try {
+      isIgnored = await gitIsIgnored({ path, filepath: normalizedFilepath });
+    } catch (e) {
+      logger.warn(
+        `Failed to check if file '${normalizedFilepath}' is ignored, proceeding with staging`,
+        e,
+      );
+    }
+    if (isIgnored) {
+      logger.debug(
+        `Skipping staging of ignored file '${normalizedFilepath}' (file is in .gitignore)`,
+      );
+      return;
+    }
+  }
+
   if (settings.enableNativeGit) {
     await execOrThrow(
       ["add", "--", normalizedFilepath],