feat(views,surface-host): Extensions sidebar view — auto-expanded surfaces + tables

views (new feature):
- pure panel-stack reducer + thin generic ViewSidebar (dropdown picker + add/remove),
  switches on view KIND, never a surface id

Extensions view (composition root):
- folds frontend modules + backend surfaces into one "Extensions" view
- frontend module list AGGREGATED from each feature's public `manifest` export
  (can't drift); no per-module version (FE features are internal to dispatch-web)
- surfaces are AUTO-SUBSCRIBED on catalog + rendered expanded (no catalog buttons)

surface-host:
- consecutive `stat` fields coalesce into one aligned label/value table (StatTable)
- generic custom-field renderer: dispatch on rendererId === "table" → SurfaceTable
  (pure parseTablePayload), so a backend `custom`/table field renders generically
- shared presentational components/Table.svelte (used by both, neither feature
  depends on the other)

store:
- auto-subscribe every catalog entry, unsubscribe vanished ones, re-subscribe all
  on reconnect; expose all received specs via `surfaces` (drops single-selection)

backend-handoff: CR-1 — emit Loaded Extensions as a custom/table field; notes
what's already covered FE-side (renderer shipped, stat-table fallback works).

1 files changed, 49 insertions, 0 deletions

diff --git a/src/features/views/logic/panels.ts b/src/features/views/logic/panels.ts
new file mode 100644
index 0000000..38c28fb
--- /dev/null
+++ b/src/features/views/logic/panels.ts
@@ -0,0 +1,49 @@
+/**
+ * Pure reducer for the view sidebar's panel stack.
+ *
+ * A "view" is the RESERVED Dispatch sidebar affordance (see GLOSSARY): the user
+ * stacks panels, each showing one view KIND chosen from a dropdown, and adds
+ * more with a `+` button. This module is the pure model — zero DOM, zero Svelte.
+ * The component (`ViewSidebar.svelte`) is a thin runes wrapper over it.
+ *
+ * `id` is a per-session stable key for `{#each}` only; it is never persisted.
+ */
+
+export interface ViewPanel {
+	readonly id: number;
+	/** Selected view-kind id, or `null` while the panel still reads "Select a view". */
+	readonly kind: string | null;
+}
+
+export interface PanelsState {
+	readonly panels: readonly ViewPanel[];
+	readonly nextId: number;
+}
+
+/**
+ * Seed state. Each entry becomes one panel in order; pass `["surfaces"]` to open
+ * a single preset panel, or `[null]` for one empty "Select a view" panel.
+ */
+export function initialPanels(kinds: readonly (string | null)[] = [null]): PanelsState {
+	let nextId = 0;
+	const panels = kinds.map((kind) => ({ id: nextId++, kind }));
+	return { panels, nextId };
+}
+
+export function addPanel(state: PanelsState, kind: string | null = null): PanelsState {
+	return {
+		panels: [...state.panels, { id: state.nextId, kind }],
+		nextId: state.nextId + 1,
+	};
+}
+
+export function removePanel(state: PanelsState, id: number): PanelsState {
+	return { ...state, panels: state.panels.filter((p) => p.id !== id) };
+}
+
+export function selectKind(state: PanelsState, id: number, kind: string | null): PanelsState {
+	return {
+		...state,
+		panels: state.panels.map((p) => (p.id === id ? { ...p, kind } : p)),
+	};
+}