Live agent todo list: compact scrollable strip above the composer

Add a todo.update frame (server->app) carrying the agent's full current
todo list. The gateway emits it whenever the hermes todo tool completes
(the tool result is authoritative even for merge writes) and re-sends a
snapshot right after hello so a reconnecting device re-learns the plan.
Ephemeral: never outboxed.

The app renders it as a compact strip above the composer (max 3 lines,
the rest scrollable) mirroring the hermes desktop composer status stack:
pending = hollow ring, in_progress = spinner, completed = green check,
cancelled = struck through. It auto-scrolls to the current task whenever
the active task changes, and hides itself once the list is empty or fully
resolved.

docs/protocol/frames.schema.json

@@ -50,6 +50,7 @@
       "tool.start": { "description": "Cosmetic per-tool emoji (resolved server-side via hermes' get_tool_emoji: active-skin overrides, then the tool registry's per-tool emoji); omitted when the tool is unknown so the app falls back to its own default glyph.", "payload": { "index": { "type": "integer" }, "name": { "type": "string" }, "preview": { "type": "string" }, "args": { "type": "object" }, "emoji": { "type": "string" } } },
       "tool.progress": { "payload": { "index": { "type": "integer" }, "name": { "type": "string" }, "note": { "type": "string" } } },
       "tool.end": { "payload": { "index": { "type": "integer" }, "name": { "type": "string" }, "ok": { "type": "boolean" }, "duration": { "type": "number" }, "output_preview": { "type": "string" } } },
+      "todo.update": { "description": "The agent's FULL current todo list for a chat/thread lane (last-write-wins). Emitted whenever the `todo` tool completes (the tool result is authoritative even for merge writes, whose args carry only the changed items) and, as a snapshot, right after hello when a device opens its event stream. Ephemeral: never outboxed, so a reconnecting device learns the list from the snapshot, not a replay. The app renders it as a compact scrollable strip above the composer.", "payload": { "todos": { "type": "array", "items": { "type": "object", "properties": { "id": { "type": "string" }, "content": { "type": "string" }, "status": { "type": "string", "enum": ["pending", "in_progress", "completed", "cancelled"] } } } } } },
       "typing": { "payload": { "on": { "type": "boolean" } } },
       "notification": { "payload": { "kind": { "type": "string", "enum": ["channel_renamed", "channel_created", "channel_deleted", "cron", "approval", "clarify", "generic"] }, "title": { "type": "string" }, "body": { "type": "string" }, "ts": { "type": "integer" } } },
       "channel.list": { "description": "Full channel directory (response to a channel.list request).", "payload": { "channels": { "type": "array", "items": { "$ref": "#/definitions/channel" } } } },