feat: add human-readable CI log output for show_full_output mode

Replace raw JSON dumps with concise, scannable log lines when
show_full_output is enabled. Adds an onMessage callback to the SDK
runner that formats each message type into 1-2 line summaries with
emoji prefixes, tool-specific parameter display, result correlation
for parallel tool calls, and subagent progress tracking.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/entrypoints/run.ts

@@ -34,6 +34,7 @@ import { installPlugins } from "../../base-action/src/install-plugins";
 import { preparePrompt } from "../../base-action/src/prepare-prompt";
 import { runClaude } from "../../base-action/src/run-claude";
 import type { ClaudeRunResult } from "../../base-action/src/run-claude-sdk";
+import { createCiOutputFormatter } from "../ci-output-formatter";
 
 /**
  * Install Claude Code CLI, handling retry logic and custom executable paths.
@@ -243,15 +244,24 @@ async function run() {
       promptFile,
     });
 
-    const claudeResult: ClaudeRunResult = await runClaude(promptConfig.path, {
-      claudeArgs: prepareResult.claudeArgs,
-      disallowedTools: process.env.DISALLOWED_TOOLS || undefined,
-      appendSystemPrompt: process.env.APPEND_SYSTEM_PROMPT,
-      model: process.env.ANTHROPIC_MODEL,
-      pathToClaudeCodeExecutable:
-        process.env.INPUT_PATH_TO_CLAUDE_CODE_EXECUTABLE,
-      showFullOutput: process.env.INPUT_SHOW_FULL_OUTPUT,
-    });
+    const showFullOutput =
+      process.env.INPUT_SHOW_FULL_OUTPUT === "true" ||
+      process.env.ACTIONS_STEP_DEBUG === "true";
+    const onMessage = showFullOutput ? createCiOutputFormatter() : undefined;
+
+    const claudeResult: ClaudeRunResult = await runClaude(
+      promptConfig.path,
+      {
+        claudeArgs: prepareResult.claudeArgs,
+        disallowedTools: process.env.DISALLOWED_TOOLS || undefined,
+        appendSystemPrompt: process.env.APPEND_SYSTEM_PROMPT,
+        model: process.env.ANTHROPIC_MODEL,
+        pathToClaudeCodeExecutable:
+          process.env.INPUT_PATH_TO_CLAUDE_CODE_EXECUTABLE,
+        showFullOutput: process.env.INPUT_SHOW_FULL_OUTPUT,
+      },
+      onMessage,
+    );
 
     claudeSuccess = claudeResult.conclusion === "success";
     executionFile = claudeResult.executionFile;