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/Program.cs

@@ -1,4 +1,5 @@
 using ClaudeDo.Data;
+using ClaudeDo.Data.Git;
 using ClaudeDo.Data.Repositories;
 using ClaudeDo.Worker.Config;
 using ClaudeDo.Worker.Hub;
@@ -25,6 +26,8 @@ builder.Services.AddSignalR();
 // Runner stack.
 builder.Services.AddSingleton<IClaudeProcess, ClaudeProcess>();
 builder.Services.AddSingleton<HubBroadcaster>();
+builder.Services.AddSingleton<GitService>();
+builder.Services.AddSingleton<WorktreeManager>();
 builder.Services.AddSingleton<TaskRunner>();
 
 // QueueService: singleton + hosted service (same instance).