feat(hooks): implement UserPromptSubmit with chat.message hook and injectHookMessage

- Add chat.message handler to createClaudeCodeHooksHook factory
- Integrate executeUserPromptSubmitHooks() for user prompt processing
- Use injectHookMessage() for file system based message injection
- Add sessionFirstMessageProcessed tracking for title generation skip
- Register chat.message hook in plugin entry point

This completes 100% port of Claude Code hooks from opencode-cc-plugin.

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

src/hooks/claude-code-hooks/index.ts

@@ -10,6 +10,11 @@ import {
   type PostToolUseContext,
   type PostToolUseClient,
 } from "./post-tool-use"
+import {
+  executeUserPromptSubmitHooks,
+  type UserPromptSubmitContext,
+  type MessagePart,
+} from "./user-prompt-submit"
 import {
   executeStopHooks,
   type StopContext,
@@ -17,10 +22,99 @@ import {
 import { cacheToolInput, getToolInput } from "./tool-input-cache"
 import { getTranscriptPath } from "./transcript"
 import { log } from "../../shared"
+import { injectHookMessage } from "../../features/hook-message-injector"
 
 export function createClaudeCodeHooksHook(ctx: PluginInput) {
+  const sessionFirstMessageProcessed = new Set<string>()
 
   return {
+    "chat.message": async (
+      input: {
+        sessionID: string
+        agent?: string
+        model?: { providerID: string; modelID: string }
+        messageID?: string
+      },
+      output: {
+        message: Record<string, unknown>
+        parts: Array<{ type: string; text?: string; [key: string]: unknown }>
+      }
+    ): Promise<void> => {
+      try {
+        const claudeConfig = await loadClaudeHooksConfig()
+        const extendedConfig = await loadPluginExtendedConfig()
+
+        const textParts = output.parts.filter((p) => p.type === "text" && p.text)
+        const prompt = textParts.map((p) => p.text ?? "").join("\n")
+
+        const isFirstMessage = !sessionFirstMessageProcessed.has(input.sessionID)
+        sessionFirstMessageProcessed.add(input.sessionID)
+
+        if (isFirstMessage) {
+          log("[Claude Hooks] Skipping UserPromptSubmit on first message for title generation")
+          return
+        }
+
+        let parentSessionId: string | undefined
+        try {
+          const sessionInfo = await ctx.client.session.get({
+            path: { id: input.sessionID },
+          })
+          parentSessionId = sessionInfo.data?.parentID
+        } catch {}
+
+        const messageParts: MessagePart[] = textParts.map((p) => ({
+          type: p.type as "text",
+          text: p.text,
+        }))
+
+        const userPromptCtx: UserPromptSubmitContext = {
+          sessionId: input.sessionID,
+          parentSessionId,
+          prompt,
+          parts: messageParts,
+          cwd: ctx.directory,
+        }
+
+        const result = await executeUserPromptSubmitHooks(
+          userPromptCtx,
+          claudeConfig,
+          extendedConfig
+        )
+
+        if (result.block) {
+          throw new Error(result.reason ?? "Hook blocked the prompt")
+        }
+
+        if (result.messages.length > 0) {
+          const hookContent = result.messages.join("\n\n")
+          const message = output.message as {
+            agent?: string
+            model?: { modelID?: string; providerID?: string }
+            path?: { cwd?: string; root?: string }
+            tools?: Record<string, boolean>
+          }
+
+          const success = injectHookMessage(input.sessionID, hookContent, {
+            agent: message.agent,
+            model: message.model,
+            path: message.path ?? { cwd: ctx.directory, root: "/" },
+            tools: message.tools,
+          })
+
+          log(
+            success
+              ? "[Claude Hooks] Hook message injected via file system"
+              : "[Claude Hooks] File injection failed",
+            { sessionID: input.sessionID }
+          )
+        }
+      } catch (error) {
+        log("[Claude Hooks] chat.message error:", error)
+        throw error
+      }
+    },
+
     "tool.execute.before": async (
       input: { tool: string; sessionID: string; callID: string },
       output: { args: Record<string, unknown> }

src/index.ts

@@ -86,6 +86,10 @@ const OhMyOpenCodePlugin: Plugin = async (ctx) => {
   return {
     tool: builtinTools,
 
+    "chat.message": async (input, output) => {
+      await claudeCodeHooks["chat.message"]?.(input, output)
+    },
+
     config: async (config) => {
       const builtinAgents = createBuiltinAgents(
         pluginConfig.disabled_agents,