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, 13 insertions, 0 deletions

diff --git a/bun.lock b/bun.lock
index e1c62d6..9b63971 100644
--- a/bun.lock
+++ b/bun.lock
@@ -18,6 +18,16 @@
         "@dispatch/kernel": "workspace:*",
       },
     },
+    "packages/cache-warming": {
+      "name": "@dispatch/cache-warming",
+      "version": "0.0.0",
+      "dependencies": {
+        "@dispatch/kernel": "workspace:*",
+        "@dispatch/session-orchestrator": "workspace:*",
+        "@dispatch/surface-registry": "workspace:*",
+        "@dispatch/ui-contract": "workspace:*",
+      },
+    },
     "packages/cli": {
       "name": "@dispatch/cli",
       "version": "0.0.0",
@@ -45,6 +55,7 @@
       "version": "0.0.0",
       "dependencies": {
         "@dispatch/auth-apikey": "workspace:*",
+        "@dispatch/cache-warming": "workspace:*",
         "@dispatch/conversation-store": "workspace:*",
         "@dispatch/credential-store": "workspace:*",
         "@dispatch/journal-sink": "workspace:*",
@@ -243,6 +254,8 @@
 
     "@dispatch/auth-apikey": ["@dispatch/auth-apikey@workspace:packages/auth-apikey"],
 
+    "@dispatch/cache-warming": ["@dispatch/cache-warming@workspace:packages/cache-warming"],
+
     "@dispatch/cli": ["@dispatch/cli@workspace:packages/cli"],
 
     "@dispatch/conversation-store": ["@dispatch/conversation-store@workspace:packages/conversation-store"],