fix(vcs): address review findings on PR #88

Findings addressed:
- F1/G1: Add doc comment to GetAllFilesInPath documenting fail-fast contract
- F2/G2: Add explicit backslash-prefix guard to skip '\ No newline' markers
- F3: Add comment explaining position > 0 guard (skip lines before first hunk)
- F4: Refactor parseHunkNewStart to use strconv.Atoi instead of per-char concat
- F5: Add error propagation tests (ListContents, GetFileContent, nested, ctx cancel)
- F6: Wrap errors.ErrUnsupported in DismissReview for programmatic checking
- S1: Add ctx.Err() checks + max file count/byte constants with clear errors
- S2: Addressed by S1 — input bounds are now enforced via the same constants

gitea/client.go

@@ -835,7 +835,7 @@ func (c *Client) ResolveComment(ctx context.Context, owner, repo string, comment
 // DismissReview dismisses a review on a pull request.
 // This is a stub for the vcs.Reviewer interface; full implementation is Phase 2.
 func (c *Client) DismissReview(ctx context.Context, owner, repo string, number int, reviewID int64, message string) error {
-	return fmt.Errorf("DismissReview: not implemented")
+	return fmt.Errorf("DismissReview: %w", errors.ErrUnsupported)
 }
 
 // GetFileContentAtRef fetches a file at a specific ref from a repo.