feat(cache-warming,surfaces,metrics,markdown): conversation-scoped surfaces, cache warming + retention, markdown

Consumes the backend cache-warming + cache-rate handoffs end-to-end and adds supporting infra:

- protocol/transport: conversation-scoped surfaces (conversationId on subscribe/invoke/surface + staleness routing); store auto-subscribes the catalog with the focused conversation and re-scopes on switch.
- surface-host: generic Number field renderer + custom rendererId dispatch (graceful skip on unknown).
- cache-warming feature: enabled toggle, min+sec interval, AUTHORITATIVE countdown from the surface's cache-warming-timer nextWarmAt, manual Warm now (POST /chat/warm), lastWarmAt-keyed history, cache-retention stat, expectedCacheRate headline.
- metrics: cross-turn expected-cache (retention) derivation + bubble badge; cache-rate fix needs no code change (inputTokens now total).
- markdown feature: marked + marked-highlight + highlight.js + dompurify, rendered in ChatView.
- fixes (gemini review): {#key activeConversationId} remount of CacheWarmingView to stop history/feedback leaking across tabs; guard NaN interval inputs from committing 0.
- docs/contracts: regenerated transport/ui-contract mirrors; backend-handoff updated (CR-3 resolved).

Verified: svelte-check 0 errors, biome clean, 494 tests pass, vite build OK.

1 files changed, 42 insertions, 3 deletions

diff --git a/src/app/App.svelte b/src/app/App.svelte
index f02797e..dae6177 100644
--- a/src/app/App.svelte
+++ b/src/app/App.svelte
@@ -1,8 +1,14 @@
 <script lang="ts">
 	import type { InvokeMessage } from "@dispatch/ui-contract";
 	import Table from "../components/Table.svelte";
+	import {
+		CacheWarmingView,
+		manifest as cacheWarmingManifest,
+		type WarmFeedback,
+	} from "../features/cache-warming";
 	import { ChatView, Composer, manifest as chatManifest, ModelSelector } from "../features/chat";
 	import { manifest as conversationCacheManifest } from "../features/conversation-cache";
+	import { manifest as markdownManifest } from "../features/markdown";
 	import { manifest as surfaceHostManifest, SurfaceView } from "../features/surface-host";
 	import { manifest as tabsManifest, TabBar } from "../features/tabs";
 	import { manifest as viewsManifest, ViewSidebar } from "../features/views";
@@ -10,15 +16,22 @@
 
 	let { store }: { store: AppStore } = $props();
 
+	// The backend's conversation-scoped cache-warming surface. Referenced by id at
+	// the composition root (sanctioned discovery-by-id) to give it a dedicated view
+	// and keep it out of the generic Extensions surface list — SurfaceView itself
+	// stays fully generic (it never switches on a surface id).
+	const CACHE_WARMING_ID = "cache-warming";
+
 	// The view kinds offered in the sidebar's dropdown. Generic data — the
 	// `viewContent` snippet below maps each kind id to its renderer.
 	const viewKinds = [
 		{ id: "model", label: "Model" },
 		{ id: "extensions", label: "Extensions" },
+		{ id: "cache-warming", label: "Cache Warming" },
 	] as const;
 
-	// Default sidebar layout: a Model panel on top, Extensions below.
-	const initialViews = ["model", "extensions"] as const;
+	// Default sidebar layout: a Model panel on top, then Extensions, then Cache Warming.
+	const initialViews = ["model", "extensions", "cache-warming"] as const;
 
 	// Frontend module list for the "Loaded Modules" view, AGGREGATED from each
 	// feature's public `manifest` export so it can't drift from what's actually
@@ -32,6 +45,8 @@
 		surfaceHostManifest,
 		viewsManifest,
 		conversationCacheManifest,
+		markdownManifest,
+		cacheWarmingManifest,
 	].map((m) => [m.name, m.description] as const);
 
 	// Right sidebar: open by default on wide screens (pushes the chat aside),
@@ -51,6 +66,19 @@
 	function handleSelectModel(model: string) {
 		store.selectModel(model);
 	}
+
+	// Adapt the store's WarmResult to the cache-warming feature's WarmNow port.
+	async function warmNow(): Promise<WarmFeedback | null> {
+		const result = await store.warmNow();
+		if (result === null) return null;
+		return result.ok
+			? {
+					ok: true,
+					cachePct: result.response.cachePct,
+					expectedCacheRate: result.response.expectedCacheRate,
+				}
+			: { ok: false, error: result.error };
+	}
 </script>
 
 <main class="relative flex h-screen overflow-hidden">
@@ -165,9 +193,20 @@
 		</section>
 		<section class="mt-4 flex flex-col gap-3">
 			<h3 class="text-xs font-semibold uppercase opacity-60">Surfaces</h3>
-			{#each store.surfaces as spec (spec.id)}
+			{#each store.surfaces.filter((s) => s.id !== CACHE_WARMING_ID) as spec (spec.id)}
 				<SurfaceView {spec} onInvoke={handleInvoke} />
 			{/each}
 		</section>
+	{:else if kind === "cache-warming"}
+		<!-- Re-mount per conversation (like ChatView) so the view's local warming
+		     history / manual-warm feedback can't bleed across tabs. -->
+		{#key store.activeConversationId}
+			<CacheWarmingView
+				spec={store.surface(CACHE_WARMING_ID)}
+				canWarm={store.activeConversationId !== null}
+				onInvoke={handleInvoke}
+				{warmNow}
+			/>
+		{/key}
 	{/if}
 {/snippet}