loading_state

After the activity bar shell mounts, the header may appear before pane data.
Cover every sequencing beat with an explicit loading or error affordance — never a blank content area:
1. HTML shell ( before Svelte boots ): inline waiting markup in get-activity-bar-html.ts.
2. Connecting: header visible; a post-first-frame `ready` handshake starts the index and requests the first host state.
3. Waiting for index: workspace_loading.
4. Ready panes: context_panes_loading and minigraph_loading.
Index sync progress belongs in workspace_pane; graph slice waits stay in miniature_graph_pane, not a second global overlay.
Host posts index health on `ready` and on subsequent status changes; soft-waits when the index is not ready instead of erroring the whole bar.

Status: done

Interactive page: loading_state