feat: add Google Gemini CLI adapter (#33)

Author: shreyas-lyzr

README.md

@@ -357,6 +357,7 @@ Adapters are used by both `export` and `run`. Available adapters:
 | `github` | GitHub Actions agent |
 | `git` | Git-native execution (run only) |
 | `opencode` | OpenCode instructions + config |
+| `gemini` | Google Gemini CLI (GEMINI.md + settings.json) |
 | `openclaw` | OpenClaw format |
 | `nanobot` | Nanobot format |
 | `cursor` | Cursor `.cursor/rules/*.mdc` files |