feat(hooks): add think-mode hook for automatic model switching

Detects thinking keywords (ultrathink, deepthink, etc.) and switches
to thinking-capable models automatically.

Supports model patterns:
- claude-sonnet-4-0 -> claude-sonnet-4-0-max-thinking
- claude-sonnet-4-20250514 -> claude-sonnet-4-20250514-max-thinking

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/hooks/think-mode/index.ts

@@ -0,0 +1,73 @@
+import { detectThinkKeyword, extractPromptText } from "./detector"
+import { getHighVariant, isAlreadyHighVariant } from "./switcher"
+import type { ThinkModeState, ThinkModeInput } from "./types"
+
+export * from "./detector"
+export * from "./switcher"
+export * from "./types"
+
+const thinkModeState = new Map<string, ThinkModeState>()
+
+export function clearThinkModeState(sessionID: string): void {
+  thinkModeState.delete(sessionID)
+}
+
+export function createThinkModeHook() {
+  return {
+    "chat.params": async (
+      output: ThinkModeInput,
+      sessionID: string
+    ): Promise<void> => {
+      const promptText = extractPromptText(output.parts)
+
+      const state: ThinkModeState = {
+        requested: false,
+        modelSwitched: false,
+      }
+
+      if (!detectThinkKeyword(promptText)) {
+        thinkModeState.set(sessionID, state)
+        return
+      }
+
+      state.requested = true
+
+      const currentModel = output.message.model
+      if (!currentModel) {
+        thinkModeState.set(sessionID, state)
+        return
+      }
+
+      state.providerID = currentModel.providerID
+      state.modelID = currentModel.modelID
+
+      if (isAlreadyHighVariant(currentModel.modelID)) {
+        thinkModeState.set(sessionID, state)
+        return
+      }
+
+      const highVariant = getHighVariant(currentModel.modelID)
+
+      if (!highVariant) {
+        thinkModeState.set(sessionID, state)
+        return
+      }
+
+      output.message.model = {
+        providerID: currentModel.providerID,
+        modelID: highVariant,
+      }
+      state.modelSwitched = true
+      thinkModeState.set(sessionID, state)
+    },
+
+    event: async ({ event }: { event: { type: string; properties?: unknown } }) => {
+      if (event.type === "session.deleted") {
+        const props = event.properties as { info?: { id?: string } } | undefined
+        if (props?.info?.id) {
+          thinkModeState.delete(props.info.id)
+        }
+      }
+    },
+  }
+}