feat(kvb-git): wrap the pkgmgr worktree and gc commands as skills

kvb-git-branch-gc becomes kvb-git-branch-cleanup and kvb-git-orphans-find becomes kvb-git-worktree-orphans, which drops its own orphans.py for pkgmgr's output. New wrappers: kvb-git-gc, kvb-git-worktree-cleanup and kvb-git-worktree-up. kvb-cleanup, kvb-dream, AGENTS.md and README.md point at the new names. Merges only after the pkgmgr release that ships these commands.

🎯 Fix: 90 %
💥 Break: 3 %
💸 Cost: new
⏱️ Time: new
🛡️ Security: 100 %
🏆 Score: 87
🚦 Gate: cost new, time new: cleared by the operator's commit word for the Skills wrappers (2026-11-07)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
(cherry picked from commit 18dade9a48a84761bf0c3a9b35584367ae0cb0e4)

tests/test_dream.py

@@ -24,7 +24,7 @@ class TestDreamSkill(unittest.TestCase):
         text = SKILL.read_text(encoding="utf-8")
         self.assertIn("name: kvb-dream", text)
         self.assertIn("multiSelect: false", text)
-        for skill in ("`kvb-optimize`", "`kvb-cleanup`", "`kvb-git-branch-gc`"):
+        for skill in ("`kvb-optimize`", "`kvb-cleanup`", "`kvb-git-gc`"):
             self.assertIn(skill, text)
 
     def test_optimize_covers_every_optimization_skill(self):