feat(cache-warming): per-conversation prompt-cache warming + warm() service

Backend-driven warming targeting whatever provider a conversation uses (incl. the
external Claude provider-anthropic). Core engine + on/off + last-cache-% done;
interval-as-view-control pending a ui-contract NumberField (surface-system gap).

Mechanism:
- kernel: expose HostAPI.emit (typed bus event emit; counterpart of on)
- session-orchestrator: turnStarted/turnSettled event hooks (conversationId/cwd/model);
  warm() service (cacheWarmHandle) reusing the real-turn assembly (byte-identical prefix,
  provider-agnostic), refuses mid-turn, never persists/emits, returns Usage
- cache-warming (new ext): per-conversation timers (arm on settle, cancel on start,
  in-flight invalidation), calls warm(), pct=round(clamp(cacheRead/input,0,1)*100),
  persists {enabled,intervalMs} (default on/240s), registers a controls surface
- host-bin: register cache-warming; transport-http: HostAPI stub +emit (fan-out)

Honors old-code invariants. 760 vitest + 109 bun = 869 tests; tsc -b EXIT 0; biome clean.

1 files changed, 14 insertions, 0 deletions

diff --git a/packages/cache-warming/package.json b/packages/cache-warming/package.json
new file mode 100644
index 0000000..eaf3fda
--- /dev/null
+++ b/packages/cache-warming/package.json
@@ -0,0 +1,14 @@
+{
+	"name": "@dispatch/cache-warming",
+	"version": "0.0.0",
+	"type": "module",
+	"private": true,
+	"main": "dist/index.js",
+	"types": "dist/index.d.ts",
+	"dependencies": {
+		"@dispatch/kernel": "workspace:*",
+		"@dispatch/session-orchestrator": "workspace:*",
+		"@dispatch/surface-registry": "workspace:*",
+		"@dispatch/ui-contract": "workspace:*"
+	}
+}