[BUG] plugin package.json drifts from config: stale deps never cleaned, missing deps cause slow startup #30526

Description

OpenCode manages plugins through two paths that are poorly synchronized:

Path 1: opencode plugin install --global — Uses @npmcli/arborist reify with save: true to append the plugin to package.json. This is append-only: it never removes entries for plugins that were previously installed but are no longer in config.

Path 2: Direct config edit + restart — Users edit opencode.json/tui.json directly and restart. On startup, Loader.resolve() calls Npm.add() for each plugin individually, which calls reify() per-plugin (no batch). If node_modules is missing or stale, each plugin triggers a separate npm resolve+install.

Over time, package.json drifts from the actual plugin declarations in config:

1. Stale deps remain — e.g. replacing @tarquinen/opencode-dcp with open-mem in config leaves the old entry in package.json forever
2. Missing deps — plugins added directly to config JSON are never added to package.json; startup must resolve them from scratch each time
3. Slow startup — each plugin calls Npm.add() → individual reify(), N plugins = N sequential npm operations instead of one batch install
4. No plugin remove command — there is no way to cleanly uninstall a plugin from both config and package.json

Reproduction

Scenario A (CLI path — stale entries):

1. opencode plugin install --global some-plugin@1.0.0 → package.json gets {"some-plugin": "1.0.0"}
2. opencode plugin install --global replacement@2.0.0 → config is updated, but some-plugin stays in package.json
3. Repeat → package.json accumulates orphaned deps

Scenario B (config edit path — missing entries + slow startup):

1. Edit ~/.config/opencode/opencode.json: add "new-plugin@^1.0.0" to plugin array
2. Delete node_modules (or start fresh)
3. Restart opencode → startup takes seconds as each plugin is resolved individually via Npm.add() → reify()
4. After startup, package.json may still not reflect all declared plugins (only the ones that needed install)

Root Cause (source analysis)

Suggested Fix

A. Sync package.json from config on startup — Before the per-plugin resolve loop, rebuild package.json dependencies to match the union of all plugin specifiers in opencode.json + tui.json, then run a single batch reify(). This would:

• Remove stale entries
• Add missing entries
• Replace N individual reify calls with one batch install

B. Add opencode plugin remove <module> command — Removes plugin from config JSON and prunes package.json entry. Gives users explicit control.

Workaround

Users experiencing long "loading plugins" delays on startup can manually clean up:

# Regenerate package.json from config, then batch install (eliminates the slow per-plugin resolve)
cd ~/.config/opencode
rm -rf node_modules package.json package-lock.json
# Restart opencode — it will regenerate from config declarations

Environment

• OpenCode: v1.15.13
• OS: macOS
• Config: global (opencode.json + tui.json)
• 8 plugins across opencode.json + tui.json