tool.start gains an optional cosmetic 'emoji' field, resolved server-side through hermes' own display layer (active-skin overrides, then the tool registry's per-tool emoji) so icons track the user's hermes theme and new/plugin tools get their glyph for free. Omitted for unknown tools so the app falls back to its default wrench. - protocol.py: tool_start(emoji=...) kwarg, payload field when set - adapter.py: _tool_emoji() helper (lazy import, None on unknown/failure) - frames.schema.json + docs/04: field documented - app: ToolStartPayload.emoji -> ToolItem.emoji -> ToolCard header - tests: frame shape, resolution/fallback, end-to-end tool.start emoji