Initial commit — Antigravity plugin v0.1.0

Plugin Claude Code miroir du plugin codex officiel d'OpenAI, mais
pour Google Antigravity (agy CLI). Headless via:

  agy --print --dangerously-skip-permissions --print-timeout 10m

Includes:
- 1 forwarder agent (antigravity-rescue)
- 5 slash commands (setup, rescue, status, result, cancel)
- 3 internal skills (cli-runtime, result-handling, gemini-prompting)
- agy-companion.mjs runtime (task / setup / status / result / cancel)
- marketplace.json for `/plugin marketplace add`

Tested: setup OK, foreground task OK, background workflow OK
(except OAuth refresh which requires interactive TTY).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

skills/gemini-prompting/SKILL.md

@@ -0,0 +1,96 @@
+---
+name: gemini-prompting
+description: Internal guidance for composing Antigravity (Gemini) prompts for coding, review, diagnosis, and research tasks inside the Antigravity Claude Code plugin
+user-invocable: false
+---
+
+# Prompting Gemini through Antigravity
+
+Antigravity wraps Google's Gemini model in a CLI. The model is verbose by default and tends to over-explain. To get great rescue/task output, follow these rules.
+
+## 1. Be explicit and structured
+
+Gemini works better when the request is well-structured. Use a header + numbered steps when possible:
+
+```
+TASK
+Investigate why <X> fails on macOS but works on Linux.
+
+CONTEXT
+- Reproduces with `npm test` in /Users/.../my-project
+- Failing test: src/utils.test.ts → "should hash file"
+- Suspected root cause: BSD `sha256sum` not installed on macOS
+
+WHAT I WANT
+1. Root-cause confirmation (read the code, run the failing test if possible)
+2. Concrete fix (with file diff)
+3. Verification command
+```
+
+## 2. Tell it what NOT to do
+
+Gemini tends to add tons of context, options, and alternatives. To keep responses tight:
+
+```
+CONSTRAINTS
+- Do not propose multiple solutions — pick the best one.
+- Do not explain what the code does at length. Focus on the fix.
+- Do not write a README/CHANGELOG/migration guide.
+- Output max 200 words of prose + the diff.
+```
+
+## 3. Provide file paths explicitly
+
+Gemini has its own scratch workspace at `~/.gemini/antigravity-cli/scratch/`. To make it work on the user's actual repo, **always provide absolute paths** in the prompt:
+
+```
+Work in /Users/olivierdupont/Desktop/diversclaude/my-project/
+Read src/utils.ts and src/utils.test.ts.
+Apply the fix to src/utils.ts.
+```
+
+If the path is outside the default workspace, add the routing flag `--add-dir /path/to/project`.
+
+## 4. Diagnosis vs. fix
+
+Distinguish clearly between:
+- **Diagnosis**: "Investigate and report. No edits."
+- **Fix**: "Apply the fix directly to the files."
+- **Plan**: "Write a plan but don't execute it."
+
+Default behavior of `--dangerously-skip-permissions` is to allow file edits. If you want read-only behavior, say so explicitly in the prompt.
+
+## 5. Resume vs. fresh
+
+Gemini's `--continue` flag resumes the most recent session. Use it (via the runtime's `--resume` flag) when:
+- Following up on a previous rescue
+- Iterating on a draft fix
+- Asking for more depth on the same investigation
+
+Use a fresh session when:
+- Completely new task, unrelated to previous
+- The previous context is stale or wrong-headed
+
+## 6. Antipatterns
+
+- **Vague**: "Fix this bug" — what bug? where?
+- **Too many sub-tasks**: keep one focused task per `task` call.
+- **Asking for opinions**: Gemini's opinions are bland — ask for actions.
+- **Trusting blindly**: ALWAYS read the resulting diff before committing.
+
+## 7. Recommended boilerplate
+
+```
+TASK: <one-sentence outcome>
+
+CONTEXT:
+<3-8 bullets of what's known, file paths, what's been tried>
+
+DELIVERABLE:
+<file diffs, verification command, or specific answer>
+
+CONSTRAINTS:
+- Output max <N> lines.
+- Do not modify files outside <list>.
+- Do not refactor anything outside the immediate fix.
+```