feat(worker,data): add git worktree support and conventional commits

GitService (in ClaudeDo.Data so the UI can reuse it) wraps the git CLI:
IsGitRepo, RevParseHead, WorktreeAdd/Remove, HasChanges, AddAll, Commit
(multi-line via -F -), DiffStat, BranchDelete, MergeFfOnly. Throws with
stderr on failure.

WorktreeManager owns the per-task lifecycle: validate working_dir is a
git repo (throws if not, no DB row written), create the worktree at
<repo>/../.claudedo-worktrees/<slug>/<id>/ (or central root per config),
insert the worktrees row. CommitIfChangedAsync skips when there are no
changes, otherwise commits and updates head_commit + diff_stat.

CommitMessageBuilder produces "{type}({list-slug}): {title<=60}" with a
blank-line-separated description (truncated to 400) and a permanent
"ClaudeDo-Task: <id>" trailer. Slug normalises whitespace + strips
non-alphanumerics. Newlines hard-coded to \n so git on Windows doesn't
choke on \r\n.

TaskRunner branches on list.WorkingDir: worktree path runs Claude in the
worktree, commits on success, broadcasts WorktreeUpdated; failure leaves
the worktree row active for inspection. Sandbox path unchanged.

Tests: 38 pass (12 new). GitRepoFixture spins up a real temp repo with a
seed commit; tests skip gracefully if `git` isn't on PATH.
CommitMessageBuilder fully unit-tested. WorktreeManager covers create,
no-change skip, real-commit, and non-repo failure.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Worker/Runner/CommitMessageBuilder.cs

@@ -0,0 +1,46 @@
+using System.Text;
+using System.Text.RegularExpressions;
+
+namespace ClaudeDo.Worker.Runner;
+
+public static class CommitMessageBuilder
+{
+    public static string Build(string commitType, string listName, string taskTitle, string? taskDescription, string taskId)
+    {
+        var slug = ToSlug(listName);
+        var title = Truncate(taskTitle, 60);
+        var header = $"{commitType}({slug}): {title}";
+
+        var sb = new StringBuilder();
+        sb.Append(header);
+
+        var hasDescription = !string.IsNullOrWhiteSpace(taskDescription);
+        if (hasDescription)
+        {
+            sb.Append("\n\n");
+            sb.Append(Truncate(taskDescription!.Trim(), 400));
+        }
+
+        // Trailer is always included.
+        sb.Append("\n\n");
+        sb.Append($"ClaudeDo-Task: {taskId}");
+
+        return sb.ToString();
+    }
+
+    public static string ToSlug(string name)
+    {
+        var lower = name.ToLowerInvariant();
+        // Replace whitespace runs with a single dash.
+        var dashed = Regex.Replace(lower, @"\s+", "-");
+        // Remove all non-alphanumeric-and-dash characters.
+        var cleaned = Regex.Replace(dashed, @"[^a-z0-9\-]", "");
+        // Collapse multiple dashes.
+        var collapsed = Regex.Replace(cleaned, @"-{2,}", "-");
+        // Trim leading/trailing dashes.
+        return collapsed.Trim('-');
+    }
+
+    private static string Truncate(string value, int maxLength) =>
+        value.Length <= maxLength ? value : value[..maxLength];
+}