fix: forward MCP_TIMEOUT, MCP_TOOL_TIMEOUT, MAX_MCP_OUTPUT_TOKENS to action step (#1162)

These three env vars are read directly from process.env by the Claude CLI
subprocess to configure MCP server behavior. Users setting them in their
workflow had no reliable way to make them reach the CLI:

- Job-level env: shadowed by the step's explicit env: block
- Step-level env: on the calling workflow step is not inherited by
  composite action steps
- GITHUB_ENV from a prior step: same shadowing problem
- settings input: writes to ~/.claude/settings.json, not process.env

The fix is to add explicit ${{ env.VAR }} passthrough lines for all three
vars, matching the existing pattern already used for OTEL_*, AWS_*, and
Vertex configuration (lines 271-317). No TypeScript changes are needed;
the forwarding chain in parse-sdk-options.ts is already correct.

Fixes #1152

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

action.yml

@@ -312,6 +312,15 @@ runs:
         ANTHROPIC_DEFAULT_HAIKU_MODEL: ${{ env.ANTHROPIC_DEFAULT_HAIKU_MODEL }}
         ANTHROPIC_DEFAULT_OPUS_MODEL: ${{ env.ANTHROPIC_DEFAULT_OPUS_MODEL }}
 
+        # MCP configuration — these env vars are read directly from process.env by the
+        # Claude CLI subprocess. They must be listed explicitly here because this step's
+        # env: block shadows the calling workflow's job-level env vars (GitHub Actions
+        # composite action behavior). Set these in your workflow's job-level env: or via
+        # a prior step that writes to $GITHUB_ENV.
+        MCP_TIMEOUT: ${{ env.MCP_TIMEOUT }}
+        MCP_TOOL_TIMEOUT: ${{ env.MCP_TOOL_TIMEOUT }}
+        MAX_MCP_OUTPUT_TOKENS: ${{ env.MAX_MCP_OUTPUT_TOKENS }}
+
         # Telemetry configuration
         CLAUDE_CODE_ENABLE_TELEMETRY: ${{ env.CLAUDE_CODE_ENABLE_TELEMETRY }}
         OTEL_METRICS_EXPORTER: ${{ env.OTEL_METRICS_EXPORTER }}