feat(ui): diff modal with file sidebar and tinted hunks

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Data/Git/GitService.cs

@@ -27,6 +27,14 @@ public sealed class GitService
             throw new InvalidOperationException($"git worktree add failed (exit {exitCode}): {stderr}");
     }
 
+    public async Task<string> GetStatusPorcelainAsync(string workingDirectory, CancellationToken ct = default)
+    {
+        var (exitCode, stdout, stderr) = await RunGitAsync(workingDirectory, ["status", "--porcelain"], ct);
+        if (exitCode != 0)
+            throw new InvalidOperationException($"git status --porcelain failed (exit {exitCode}): {stderr}");
+        return stdout;
+    }
+
     public async Task<bool> HasChangesAsync(string worktreePath, CancellationToken ct = default)
     {
         var (exitCode, stdout, stderr) = await RunGitAsync(worktreePath, ["status", "--porcelain"], ct);
@@ -50,6 +58,21 @@ public sealed class GitService
             throw new InvalidOperationException($"git commit failed (exit {exitCode}): {stderr}");
     }
 
+    public async Task<string> GetDiffAsync(string worktreePath, CancellationToken ct = default)
+    {
+        var (exitCode, stdout, stderr) = await RunGitAsync(worktreePath,
+            ["diff", "HEAD"], ct);
+        if (exitCode != 0)
+            throw new InvalidOperationException($"git diff HEAD failed (exit {exitCode}): {stderr}");
+        // If nothing staged vs HEAD, try the index (untracked is never in diff)
+        if (string.IsNullOrWhiteSpace(stdout))
+        {
+            var (e2, s2, _) = await RunGitAsync(worktreePath, ["diff", "--cached"], ct);
+            if (e2 == 0) return s2;
+        }
+        return stdout;
+    }
+
     public async Task<string> DiffStatAsync(string worktreePath, string baseCommit, string headCommit, CancellationToken ct = default)
     {
         var (exitCode, stdout, stderr) = await RunGitAsync(worktreePath,