Chores: claim from the pool; admin picks who appears on the family board

- "Anyone" chores get Take it / Put back; a claimed chore is that person's for the day
- Per-person "Show on the family board" switch controls board tiles and family chore progress
- Tests and README updated

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

users.js

@@ -61,6 +61,7 @@ function update(id, patch) {
     u.disabled = d; u.epoch++; // disabling also signs them out everywhere
   }
   if (patch.kid !== undefined) { const k = require('./kidlimits').cleanKid(patch.kid); if (u.role === 'admin' && k && k.on) throw new Error('An admin cannot be a child account'); if (k) u.kid = k; else delete u.kid; }
+  if (patch.board !== undefined) { if (patch.board === false) u.board = false; else delete u.board; } // whether they are on the family board and in family chore progress
   if (patch.signOutEverywhere) u.epoch++;
   save(); return u;
 }
@@ -74,7 +75,7 @@ function remove(id) {
 
 const can = (u, tab) => !!u && (ALWAYS.includes(tab) || u.role === 'admin' || (u.tabs || []).includes(tab));
 const allowedTabs = u => !u ? [] : [...ALWAYS, ...(u.role === 'admin' ? TABS : (u.tabs || []).filter(t => TABS.includes(t)))];
-const publicView = u => ({ id: u.id, name: u.name, role: u.role, tabs: allowedTabs(u), disabled: !!u.disabled, created: u.created, ...(u.kid && u.kid.on ? { kid: u.kid } : {}) });
+const publicView = u => ({ id: u.id, name: u.name, role: u.role, tabs: allowedTabs(u), disabled: !!u.disabled, created: u.created, ...(u.kid && u.kid.on ? { kid: u.kid } : {}), board: u.board !== false });
 
 // ---- A single-user install becomes "the admin" without anyone doing anything: their passkey, tasks, events, settings,
 // iCloud connection and calendar links move into their own folder. (Copied, so the originals stay as a backup.)