fix: add model parameter support to base-action

- Add model field to ClaudeOptions type
- Pass ANTHROPIC_MODEL env var to runClaude function
- Handle --model argument in prepareRunConfig

This allows the model specified in action.yml to be properly passed
to the Claude CLI command.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

base-action/src/index.ts

@@ -26,6 +26,7 @@ async function run() {
       appendSystemPrompt: process.env.INPUT_APPEND_SYSTEM_PROMPT,
       claudeEnv: process.env.INPUT_CLAUDE_ENV,
       fallbackModel: process.env.INPUT_FALLBACK_MODEL,
+      model: process.env.ANTHROPIC_MODEL,
     });
   } catch (error) {
     core.setFailed(`Action failed with error: ${error}`);

base-action/src/run-claude.ts

@@ -21,6 +21,7 @@ export type ClaudeOptions = {
   claudeEnv?: string;
   fallbackModel?: string;
   timeoutMinutes?: string;
+  model?: string;
 };
 
 type PreparedConfig = {
@@ -94,6 +95,9 @@ export function prepareRunConfig(
   if (options.fallbackModel) {
     claudeArgs.push("--fallback-model", options.fallbackModel);
   }
+  if (options.model) {
+    claudeArgs.push("--model", options.model);
+  }
   if (options.timeoutMinutes) {
     const timeoutMinutesNum = parseInt(options.timeoutMinutes, 10);
     if (isNaN(timeoutMinutesNum) || timeoutMinutesNum <= 0) {