fix: resolve publish blockers for v3.7.4→v3.8.0 release

- Fix #1991 crash: optional chaining for task-history sessionID access
- Fix #1992 think-mode: add antigravity entries to HIGH_VARIANT_MAP
- Fix #1949 Copilot premium misattribution: use createInternalAgentTextPart
- Fix #1982 load_skills: pass directory to discoverSkills for project-level skills
- Fix command priority: sort scopePriority before .find(), project-first return
- Fix Google provider transform: apply in userFallbackModels path
- Fix ralph-loop TUI: optional chaining for event handler
- Fix runtime-fallback: unify dual fallback engines, remove HTTP 400 from retry,
  fix pendingFallbackModel stuck state, add priority gate to skip model-fallback
  when runtime-fallback is active
- Fix Prometheus task system: exempt from todowrite/todoread deny
- Fix background_output: default full_session to true
- Remove orphan hooks: hashline-edit-diff-enhancer (redundant with hashline_edit
  built-in diff), task-reminder (dead code)
- Remove orphan config entries: 3 stale hook names from Zod schema
- Fix disabled_hooks schema: accept arbitrary strings for forward compatibility
- Register json-error-recovery hook in tool-guard pipeline
- Add disabled_hooks gating for question-label-truncator, task-resume-info,
  claude-code-hooks
- Update test expectations to match new behavior

src/plugin/chat-message.ts

@@ -45,6 +45,24 @@ export function createChatMessageHandler(args: {
   output: ChatMessageHandlerOutput
 ) => Promise<void> {
   const { ctx, pluginConfig, firstMessageVariantGate, hooks } = args
+  const pluginContext = ctx as {
+    client: {
+      tui: {
+        showToast: (input: {
+          body: {
+            title: string
+            message: string
+            variant: "warning"
+            duration: number
+          }
+        }) => Promise<unknown>
+      }
+    }
+  }
+  const isRuntimeFallbackEnabled =
+    hooks.runtimeFallback !== null &&
+    hooks.runtimeFallback !== undefined &&
+    (pluginConfig.runtime_fallback?.enabled ?? true)
 
   return async (
     input: ChatMessageInput,
@@ -58,7 +76,9 @@ export function createChatMessageHandler(args: {
       firstMessageVariantGate.markApplied(input.sessionID)
     }
 
-    await hooks.modelFallback?.["chat.message"]?.(input, output)
+    if (!isRuntimeFallbackEnabled) {
+      await hooks.modelFallback?.["chat.message"]?.(input, output)
+    }
     const modelOverride = output.message["model"]
     if (
       modelOverride &&
@@ -86,7 +106,7 @@ export function createChatMessageHandler(args: {
     }
 
     if (!hasConnectedProvidersCache()) {
-      ctx.client.tui
+      pluginContext.client.tui
         .showToast({
           body: {
             title: "⚠️ Provider Cache Missing",
@@ -130,6 +150,6 @@ export function createChatMessageHandler(args: {
       }
     }
 
-    applyUltraworkModelOverrideOnMessage(pluginConfig, input.agent, output, ctx.client.tui, input.sessionID)
+    applyUltraworkModelOverrideOnMessage(pluginConfig, input.agent, output, pluginContext.client.tui, input.sessionID)
   }
 }