refactor(claude-do): refactor(worker): move the merge and worktree MCP tools out

`src/ClaudeDo.Worker/External/ExternalMcpService.cs` ist **1897 Zeilen** (nachgezählt 2026-09-02; die Datei ist seit dem Anlegen dieses Tasks von 1696 weiter gewachsen): ~30 DTO-Records oben plus ~25 Tool-Methoden — während **13** Geschwisterdateien `*McpTools.cs` im selben Ordner das Topic-Split-Muster schon tragen (`ListMcpTools`, `ConfigMcpTools`, `BatchMcpTools`, `NotesMcpTools`, `QueueStateMc

ClaudeDo-Task: 1862e160-ffde-4a50-aa03-bb7251f56088

tests/ClaudeDo.Worker.Tests/External/_finalize_remainder.py

@@ -0,0 +1,54 @@
+import re
+
+path = r"C:\Private\.claudedo-worktrees\claude-do\1862e160-ffde-4a50-aa03-bb7251f56088\tests\ClaudeDo.Worker.Tests\External\_remainder.cs"
+with open(path, encoding='utf-8') as f:
+    lines = f.readlines()
+
+def idx(marker, start=0):
+    for i in range(start, len(lines)):
+        if marker in lines[i]:
+            return i
+    raise AssertionError(f"marker not found: {marker!r}")
+
+# Each deletion described as (start_marker, end_marker_exclusive) -- delete from the line
+# containing start_marker up to (but not including) the line containing end_marker.
+deletions = [
+    ("// ── GetTaskWorktree ──", "// ── GetTaskConfig ──"),
+    ("// ── MergeTask allowWaitingForReview ──", "// ── leaveConflictsInTree ──"),
+    ("// Three edits spread far enough apart", "[Fact]"),  # multi-hunk helpers, up to next [Fact]
+    ("// ── continue_merge / abort_merge ──", "// ── PreviewMerge / PreviewMergeSet ──"),
+    ("private async Task<string> CreateActiveWorktreeAsync(", "[Fact]"),
+]
+
+# Apply deletions from bottom to top so earlier indices stay valid.
+spans = []
+for start_marker, end_marker in deletions:
+    s = idx(start_marker)
+    e = idx(end_marker, s + 1)
+    spans.append((s, e))
+
+spans.sort(reverse=True)
+for s, e in spans:
+    del lines[s:e]
+
+text = ''.join(lines)
+
+# Drop the now-unused `maintenance` local + ctor arg in BuildSut(QueueService, IVerifyCommandRunner).
+before = text
+text = text.replace(
+    "        var maintenance = new WorktreeMaintenanceService(factory, git, NullLogger<WorktreeMaintenanceService>.Instance);\n",
+    "", 1)
+assert text != before, "maintenance local not removed"
+before = text
+text = text.replace(
+    "            git, factory, maintenance, merge, planningMerge,\n",
+    "            git, factory, merge, planningMerge,\n", 1)
+assert text != before, "maintenance ctor arg not removed"
+
+# Collapse any remaining runs of 2+ blank lines down to a single blank line (cosmetic only).
+text = re.sub(r'\n{3,}', '\n\n', text)
+
+with open(path, 'w', encoding='utf-8') as f:
+    f.write(text)
+
+print("final line count:", len(text.splitlines()))