refactor(agent-sync): remove 'gemini' from agent registry

bin/agent-sync.mjs

@@ -71,7 +71,6 @@ const AGENT_REGISTRY = [
   { name: 'codex',      base: homeDir('.codex'),             skillsSub: 'skills' },
   { name: 'opencode',   base: homeDir('.opencode'),          skillsSub: 'skills' },
   { name: 'cursor',     base: homeDir('.cursor'),            skillsSub: 'skills' },
-  { name: 'gemini',     base: homeDir('.gemini'),            skillsSub: 'skills' },
   { name: 'trae',       base: homeDir('.trae'),              skillsSub: 'skills' },
   { name: 'windsurf',   base: homeDir('.windsurf'),          skillsSub: 'skills' },
   { name: 'aider-desk', base: homeDir('.aider-desk'),        skillsSub: 'skills' },