Add a dayTintProvider plugin hook

Lets a plugin colour-code days in the Plan sidebar. trip-segments can
already announce "Kanazawa begins" in the day plan, but it can't make
day 12 look like it belongs to Kanazawa.

dayScheduleProvider can't cover this: it renders a fixed row, and it's
capped at 60 items per provider, so one item per day would tint the
first 60 days of a six-month trip and silently stop. This hook is
bounded by day count instead.

GET /api/day-tints/:tripId returns per-day tones for three regions of a
day card - the number badge (also the mobile day chip), the header row,
and the expanded activity list. `tone` is a shorthand filling every
region a contribution doesn't name; unnamed regions render as they do
today. Tones only, never hex, so the host can pick the alpha per theme
and per region.

One contribution per day, resolved whole: first entry wins within a
provider, first granted provider wins across plugins.

plugin-sdk/src/cli/ui.ts

@@ -218,6 +218,7 @@ export const PERMISSION_FAMILIES: PermissionFamily[] = [
       { value: 'hook:map-layer-provider', hint: 'Draw routes, corridors and zones on the trip map' },
       { value: 'hook:route-provider', hint: 'Offer routing profiles the planner can route days with (e.g. EV with charging stops)' },
       { value: 'hook:day-schedule-provider', hint: 'Attach time contributions to the day plan (charging, security, buffers)' },
+      { value: 'hook:day-tint-provider', hint: 'Colour-code days in the day plan (e.g. which leg of the trip each day belongs to)' },
       { value: 'hook:pdf-section-provider', hint: 'Add a section to the exported trip PDF' },
       { value: 'hook:atlas-layer-provider', hint: 'Add a layer to the Atlas map' },
       { value: 'hook:journal-entry-provider', hint: 'Contribute entries to a journey' },

plugin-sdk/src/index.ts

@@ -585,6 +585,42 @@ export interface DayScheduleProvider {
   getSchedule(tripId: number, ctx: PluginContext): Promise<DayScheduleContribution[]>;
 }
 
+/** A colour the host paints into one day card in the Plan sidebar (and into that day's
+ * mobile chip) — so a trip split into legs shows its leg membership while you scroll
+ * the itinerary. Tone only, never a hex: the host picks the alpha per theme AND per
+ * region, so the tint stays subtle and readable in both light and dark.
+ *
+ * The card has three separately tintable regions. Set `tone` to colour all of them,
+ * or name regions individually for finer control — e.g. a bold badge marking the leg
+ * with the activity list left plain, so a dense day stays easy to read. */
+export interface DayTintContribution {
+  dayId: number;              // must be a day of the requested trip
+  /** Shorthand: tints every region you do NOT name below. Omit it and only the
+   *  regions you name are tinted. */
+  tone?: ContributionTone;
+  /** The day-number badge — the smallest, boldest mark. Also tints the mobile day chip. */
+  badgeTone?: ContributionTone;
+  /** The day header row (number, title, date, cost). Its hover state deepens the tint. */
+  headerTone?: ContributionTone;
+  /** The expanded activity list — places, bookings and transport for the day. The
+   *  largest surface and the one behind the densest text, so it is tinted faintest. */
+  activityTone?: ContributionTone;
+  label?: string;             // optional tooltip on the day (≤60 chars)
+}
+export interface DayTintProvider {
+  /** Return one tint per day you want coloured — the natural cap is the trip's day
+   * count, so this scales to a six-month itinerary where a per-day dayScheduleProvider
+   * item would hit the ≤60 limit. Runs with the current user bound, on a short
+   * timeout; a failing call is skipped.
+   *
+   * A day takes at most one contribution — it is resolved whole, per day, never
+   * per region. Within your own list the first entry for a day wins; across plugins
+   * the first granted provider wins. Both are deterministic, so a day never flickers
+   * between two colours, and two plugins can never each own part of one card.
+   * Needs `hook:day-tint-provider`. */
+  getDayTints(tripId: number, ctx: PluginContext): Promise<DayTintContribution[]>;
+}
+
 /** A text-only section the host appends to a trip's PDF export. Declarative only —
  * plain strings the host lays out and escapes; no markup ever reaches the document. */
 export interface PdfSection {
@@ -703,6 +739,7 @@ export interface PluginDefinition {
     mapLayerProvider?: MapLayerProvider;
     routeProvider?: RouteProvider;
     dayScheduleProvider?: DayScheduleProvider;
+    dayTintProvider?: DayTintProvider;
     pdfSectionProvider?: PdfSectionProvider;
     atlasLayerProvider?: AtlasLayerProvider;
     journalEntryProvider?: JournalEntryProvider;

plugin-sdk/src/manifest.ts

@@ -89,7 +89,7 @@ export const KNOWN_PERMISSIONS = [
   'db:meta',
   'ws:broadcast:trip', 'ws:broadcast:user',
   'hook:photo-provider', 'hook:calendar-source', 'hook:place-detail-provider', 'hook:trip-warning-provider',
-  'hook:table-contributor', 'hook:map-marker-provider', 'hook:map-layer-provider', 'hook:route-provider', 'hook:day-schedule-provider', 'hook:pdf-section-provider', 'hook:atlas-layer-provider',
+  'hook:table-contributor', 'hook:map-marker-provider', 'hook:map-layer-provider', 'hook:route-provider', 'hook:day-schedule-provider', 'hook:day-tint-provider', 'hook:pdf-section-provider', 'hook:atlas-layer-provider',
   'hook:journal-entry-provider', 'hook:trip-card-provider', 'hook:notification-channel', 'hook:user-data',
   'events:subscribe', 'jobs:run', 'http:outbound',
   'weather:read', 'rates:read', 'notify:send', 'ai:invoke', 'oauth:client',

plugin-sdk/src/permissions.ts

@@ -28,6 +28,7 @@ export const HOOK_PERMISSION: Readonly<Record<string, string>> = {
   mapLayerProvider: 'hook:map-layer-provider',
   routeProvider: 'hook:route-provider',
   dayScheduleProvider: 'hook:day-schedule-provider',
+  dayTintProvider: 'hook:day-tint-provider',
   pdfSectionProvider: 'hook:pdf-section-provider',
   atlasLayerProvider: 'hook:atlas-layer-provider',
   journalEntryProvider: 'hook:journal-entry-provider',