OpenCode-Muse: Use Meta AI's Muse Code Subscription in OpenCode

An OpenCode plugin that lets OpenCode and OpenChamber use a Muse Code subscription while authentication and inference stay inside the official Muse Code CLI (muse serve, via @muse-code/sdk), with no subscription credential extracted, cached, or injected into OpenCode. Users add the published package to their opencode.jsonc, sign in with muse login, restart, and pick a Muse model; billing defaults to the Contributor lane with an opt-out to Standard via the OPENCODE_MUSE_CONTRIBUTOR_MODE environment variable. The plugin supports text, image, video, audio (transcribed via muse voice transcribe), and PDF attachments, per-model reasoning effort, conversational answers to Muse permission prompts and option-questions, and per-session worktrees where the CLI supports them.