notes: color leaves the model, the wire and all three surfaces

Step 3 of M315, and the destructive half. Steps 1 and 2 stopped every read of
this field: a card is one neutral surface per theme, and the only coloured
thing on a board is a tag. What was left was a column written by a picker and
read by nothing.

Rule 22 — the old path comes out completely. No flag, no fallback, no
"override if set".

Server: the column, the `?color=` facet, the create/update/serialise paths,
the sync assignment, the front-matter line, and Keep's colour map. Alembic
0029 drops it and sweeps `"color"` out of stored saved-filter params — a view
that silently filtered on a field the app no longer has would return nothing
and never say why. That sweep is Python, not `params::jsonb - 'color'`,
because Postgres has no try-cast and one malformed blob would abort a
migration that is running over somebody's saved views.

`NOTE_COLORS` moves from `models/note.py` to `colors.py`. A palette defined on
the model that lost one is an invitation to put the column back; labels still
name a colour, so the vocabulary belongs where the normalizer already is.

Core: the field, the facet, the `NoteCreateInput`, and every read and write in
store/push/pull. Local schema v9 drops the column and does the same
saved-filter sweep, guarded on `json_valid` so a corrupt blob loses a key
rather than becoming NULL. The uniffi layer drops `NoteEdit::Color` and
`NoteDraft.color` with it.

Web: `ColorPicker.vue`, the per-card swatch popover and its stylesheet rule,
the FilterBar colour row, the facet in the query round-trip, and the colour
half of the editor's baseline-and-save. Android: the `ColorSheet`, the
`Picker.COLOR` case, the toolbar's swatch dot, `EditorAction.SetColor`.

## The protocol: v4, and the floor deliberately stays at 3

Checked against `compat.rs` and the push handler rather than trusting the
`#[serde(default)]` annotation, because the v2 precedent points the other way:
v2 dropped `kind` and `title` and DID raise both floors, on the rule that
dropping a field a client sends and expects back is breaking.

`color` fails the second half of that test. A v3 client reading a v4 note gets
`"default"` from its own serde default and draws the colour it derives
locally — the board it drew yesterday. A v3 client pushing `color` has the key
ignored, since `_assign_note_fields` reads its payload key by key and never
validates the shape. Neither direction errors and neither shows anything
wrong. `title` was the note's NAME; this is a field that no longer renders.

So `SYNC_PROTOCOL_VERSION` and `CLIENT_PROTOCOL_VERSION` go to 4, and both
floors stay at 3. `docs/sync.md` carries the reasoning and the per-version
history, and its push example is brought back in line — it still listed
`title`, `kind` and `items`, all gone before this.

Import stays tolerant: a pre-M315 export or a Keep takeout carrying `color:`
imports fine, the key simply read past. Old exports must still import.

#3041

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/stores/notes.ts

@@ -2,14 +2,12 @@ import { defineStore } from "pinia";
 import { ref } from "vue";
 import { repo } from "../adapters";
 import { useUiStore } from "./ui";
-import type { NoteColor } from "../notes/colors";
 
 export type NoteView = "active" | "archived" | "trash";
 // Combinable facet filters for the board (mirrors the GET /api/notes query + a saved
 // view's stored params). All optional; empty = the plain, unfiltered board.
 export interface NoteFacets {
   q?: string;
-  color?: string;
   label?: string[];
   has_reminder?: boolean;
   has_attachment?: boolean;
@@ -70,7 +68,6 @@ export interface Note {
   // (server-derived). Every note has one, so every note has something to be called.
   display_title: string;
   body: string;
-  color: NoteColor;
   position: number;
   pinned: boolean;
   archived: boolean;
@@ -136,11 +133,7 @@ export const useNotesStore = defineStore("notes", () => {
     }
   }
 
-  async function create(input: {
-    body: string;
-    color: NoteColor;
-    items?: string[];
-  }): Promise<Note> {
+  async function create(input: { body: string; items?: string[] }): Promise<Note> {
     const note = await repo.notes.create(input);
     reconcile(note);
     return note;
@@ -148,9 +141,7 @@ export const useNotesStore = defineStore("notes", () => {
 
   async function mutate(
     id: string,
-    changes: Partial<
-      Pick<Note, "body" | "color" | "pinned" | "archived" | "remind_at" | "recurrence">
-    >,
+    changes: Partial<Pick<Note, "body" | "pinned" | "archived" | "remind_at" | "recurrence">>,
   ): Promise<void> {
     reconcile(await repo.notes.update(id, changes));
   }
@@ -161,10 +152,9 @@ export const useNotesStore = defineStore("notes", () => {
     if (archived)
       useUiStore().showToast("Note archived", { label: "Undo", run: () => void setArchived(id, false) });
   };
-  const setColor = (id: string, color: NoteColor) => mutate(id, { color });
   const setReminder = (id: string, remindAt: string | null) => mutate(id, { remind_at: remindAt });
   const setRecurrence = (id: string, recurrence: string | null) => mutate(id, { recurrence });
-  const saveEdit = (id: string, changes: { body: string; color: NoteColor }) => mutate(id, changes);
+  const saveEdit = (id: string, changes: { body: string }) => mutate(id, changes);
 
   async function completeReminder(id: string): Promise<void> {
     reconcile(await repo.notes.completeReminder(id));
@@ -279,7 +269,6 @@ export const useNotesStore = defineStore("notes", () => {
     create,
     setPinned,
     setArchived,
-    setColor,
     setReminder,
     setRecurrence,
     completeReminder,