feat: F5.2 sign-in with the dashboard's ticket and the service way

Server F checks the dashboard's entry ticket as itsdangerous does
(tools/ticket-oracle: tickets made by itsdangerous 2.2.0 itself), redeems
it at /__auth for a session cookie (only the key's SHA-256 is kept) and
decides at /sync by the session's grant: none, read or write; a frozen
project is read by everyone; every refusal names its reason (one list in
packages/protocol/src/sync.ts). A WebSocket from a page of another origin
is refused. /svc/* with the service key makes, deletes, freezes and
thaws projects, ends a person's grant or all their sessions (connections
let go) and lists the sessions. Snapshots, restoring and copying move to
F6 (they need the canonical doc.json and an epoch).

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

packages/protocol/src/index.ts

@@ -1,6 +1,7 @@
 // Public surface of the wire protocol.
 export * from './host.js';
 export * from './sim.js';
+export * from './sync.js';
 export * from './terminal.js';
 export * from './dns.js';
 export * from './echo.js';

packages/protocol/src/sync.ts

@@ -0,0 +1,37 @@
+// What F tells an editor about its place in a shared document (/sync, plan
+// §5, §8.5) besides the document itself — the one list both sides import:
+// why a connection is refused, why F lets it go, and the message that its
+// access changed while it is connected (a project frozen or thawed).
+
+/** Why F refuses a connection to a project (Hocuspocus' permission-denied, with this as its reason). */
+export const SYNC_REFUSALS = [
+  /** The name is not a project's id. */
+  'notAProject',
+  /** No session (no cookie, or it ran out): the dashboard issues a new ticket. */
+  'notSignedIn',
+  /** A session, but no access to this project (never had one, or it was revoked). */
+  'noAccess',
+  /** F does not know the project (deleted). */
+  'unknownProject',
+] as const;
+export type SyncRefusal = (typeof SYNC_REFUSALS)[number];
+
+/** Why F closes a connection (Hocuspocus' close, with this as its reason). */
+export const SYNC_CLOSINGS = [
+  /** The person's access to the project was taken away. */
+  'revoked',
+  /** The project was deleted. */
+  'deleted',
+] as const;
+export type SyncClosing = (typeof SYNC_CLOSINGS)[number];
+
+export const SYNC_PROTOCOL_VERSION = 1;
+
+/** A stateless message from F: the connection's access now (sent when it changes on a connection that stays). */
+export interface AccessMessage {
+  readonly v: 1;
+  readonly kind: 'access';
+  readonly readOnly: boolean;
+  /** The project is frozen (its deadline passed): no one writes, whatever their level. */
+  readonly frozen: boolean;
+}