Add per-peer auto-accept, disconnect, copy snip, and add-by-ID

- Auto-accept toggle per trusted peer (keyring.autoAccept); only
  activates when peer is cryptographically verified — unverified
  connections always prompt regardless of setting
- Disconnect button on connected screen returns to idle with full
  state reset
- Copy snip: copies own peer ID as a flit-peer:<base64> string for
  sharing out-of-band (no QR needed for initial pairing)
- Add peer by ID: paste a raw hex peer ID or flit-peer: snip in
  Invite new tab to add directly to keyring and connect without QR
- Own peer ID always visible at bottom of idle screen
- Restructured known-device row for mobile: secondary actions
  (Auto/Rename/Forget) on top line, Connect full-width below

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pwa/src/pairing/keyring.ts

@@ -5,6 +5,7 @@ export interface TrustedPeer {
   id: string // hex Ed25519 pubkey
   label: string
   addedAt: number
+  autoAccept?: boolean
 }
 
 const KEY = 'flit_keyring'
@@ -19,6 +20,11 @@ export function addTrusted(id: string, label: string): void {
   localStorage.setItem(KEY, JSON.stringify(peers))
 }
 
+export function setAutoAccept(id: string, value: boolean): void {
+  const peers = listTrusted().map(p => p.id === id ? { ...p, autoAccept: value } : p)
+  localStorage.setItem(KEY, JSON.stringify(peers))
+}
+
 export function removeTrusted(id: string): void {
   localStorage.setItem(KEY, JSON.stringify(listTrusted().filter(p => p.id !== id)))
 }
@@ -26,3 +32,7 @@ export function removeTrusted(id: string): void {
 export function isTrusted(id: string): boolean {
   return listTrusted().some(p => p.id === id)
 }
+
+export function shouldAutoAccept(id: string): boolean {
+  return listTrusted().some(p => p.id === id && p.autoAccept === true)
+}