Add Gemini CLI extension commands

[bestlux]

Summary

• add a Gemini CLI extension manifest and /codex:* command wrappers that call the existing local Codex companion runtime
• add a gemini-command.mjs bridge so Gemini slash-command args are forwarded into codex-companion.mjs with the current workspace
• harden Windows command launching for npm-shim CLIs and update the test fixtures/docs for Gemini usage

Validation

• node --test tests/commands.test.mjs
• direct fake-runtime checks for setup, review, and review --base main via codex-companion.mjs / gemini-command.mjs
• local Gemini smoke test: gemini extensions link ., gemini extensions list
• local Codex smoke test: node plugins/codex/scripts/gemini-command.mjs setup .
• local wrapper job lifecycle smoke test: review --base main, status, cancel

Local test:

[dkundel-openai]

Thank you for your contribution @bestlux! Will take a look at in in the coming days and give it a spin with the Gemini CLI

[bestlux]

Thank you for your contribution @bestlux! Will take a look at in in the coming days and give it a spin with the Gemini CLI

testing locally still - codex was gungho and opened the PR right away 😅

[bestlux]

should be in a good spot now 👍

[sachinbytecodes-lab]

yes this is better now