[Suggestion] Migrate model-usage plugin to OpenCode v2 #47

Is your feature request related to a problem? Please describe.

The plugin currently targets the legacy OpenCode plugin API. OpenCode v2 changes plugin entrypoints, TUI APIs, configuration, event handling, storage, and server hooks.

Affected areas include:

• model-usage.tsx
• model-usage-server.ts
• model-usage/sidebar.tsx
• model-usage/usage.tsx
• model-usage/analyze.tsx
• model-usage/wlib/
• Global tui.json and opencode.json
• The related persona-injector plugin

Describe the solution you'd like

Migrate the plugin to the OpenCode v2 API while preserving as much functionality as possible.

Implementation plan:

• Replace legacy server exports with Plugin.define({ id, setup }).
• Replace legacy server hook registration with v2 session.hook and tool.hook.
• Replace experimental.chat.system.transform with the v2 context hook where possible.
• Decide how to handle system snapshot ordering and final prompt capture.
• Replace tool.definition capture or remove the Tool Defs feature if no supported v2 API exists.
• Replace the { id, tui } TUI module with the v2 CLI plugin setup API.
• Replace api.slots.register with context.ui.slot.
• Replace api.keymap.registerLayer with context.keymap.layer.
• Update command metadata and slash-command definitions.
• Replace legacy dialog APIs with context.ui.dialog.show, set, and clear.
• Update wlib keymap, dialog, theme, and export helpers.
• Replace api.state and api.event usage with v2 context.data.
• Update event names and payload handling.
• Replace direct internal SQLite reads with supported v2 client/data APIs.
• Review plugin-owned JSON persistence and migrate to v2 storage where appropriate.
• Preserve or redesign the shared persona-injector system snapshot contract.
• Replace tui.json registration with v2 opencode.json, cli.json, or plugins/tui/ discovery.
• Migrate legacy configuration keys such as agent, provider, permission, and MCP registration as required by v2.
• Add or update package metadata if the plugin is distributed as an npm package.
• Run unit tests and typechecking.
• Verify loading and behavior with the exact opencode2 beta build.
• Verify /usage, /analyze, sidebar rendering, keyboard shortcuts, exports, and quota fetching.

Acceptance criteria

• The plugin loads without legacy API warnings or errors in opencode2.
• /usage and /analyze remain available.
• Sidebar usage and quota indicators render correctly.
• Dialog navigation, resizing, scrolling, exports, and shortcuts work.
• Historical usage data works without relying on unstable internal database paths.
• Unsupported features are documented clearly.
• Existing tests pass.

Additional context

The v2 documentation is currently beta and may change:

• https://opencode.ai/v2/docs/plugins
• https://opencode.ai/v2/docs/build/plugins
• https://opencode.ai/v2/docs/build/plugins/cli

The tool.definition hook and exact final system-prompt observation semantics appear to have no direct v2 equivalent and require explicit design decisions.