Trip Doctor is the companion example for the provider hooks and entity metadata added in #1429. It shows how a plugin can contribute data that TREK renders natively, instead of shipping its own iframe widget.

What it does

Warnings — scans the open trip and flags places with no map location, plus a tip when the trip has no bookings yet. These appear as a non-blocking banner at the top of the trip planner (via the warningProvider hook).
Place notes — pin a private note on any place; it shows up as a "Note" row at the foot of the place-detail panel (via the placeDetailProvider hook). Notes are stored in the plugin's own per-plugin metadata (ctx.meta), not in a schema fork.
POST /pin { placeId, note } — set or clear a place's note. Call it from a companion widget, a keyboard shortcut, or curl.

Permissions

Permission	Why
`db:read:trips`	Read the trip's places + reservations to find gaps. Membership-checked by the host — the plugin only ever sees a trip the current user can access.
`db:meta`	Store/read the plugin's own note on a place. Isolated to this plugin; writes require the user's `place_edit` permission.
`hook:trip-warning-provider`	Contribute the validation warnings shown in the planner.
`hook:place-detail-provider`	Contribute the "Note" row shown on a place.

No network access. Every read and write is bound by the host to the person viewing the planner — Trip Doctor never passes a user id, and a hook that errors or runs long is dropped without affecting the planner.

Run it

npx @trek/plugin-sdk dev      # hot-reload against a local TREK
npx @trek/plugin-sdk pack     # build a signed .trekplugin bundle

See the Plugin Cookbook for the individual recipes this example is built from.