[WIP] Fix Copilot CLI silent exit with code 1 in v0.67.3

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

---

This section details on the original issue you should resolve

<issue_title>Copilot CLI exits with code 1 silently when compiled with v0.67.3 (pre-release)</issue_title>
<issue_description>## Summary

Workflows compiled with gh-aw v0.67.3 (pre-release) fail silently — the Copilot CLI exits with code 1 after ~5 seconds, producing zero output. The same workflow compiled with v0.67.1 (latest stable) works fine.

Reproduction

1. Create a minimal workflow:

---
description: Minimal test workflow
engine:
  id: copilot
on:
  workflow_dispatch:
permissions:
  contents: read
tools:
  bash: true
safe-outputs:
  noop:
timeout-minutes: 5
---

Say "Hello from gh-aw!" and then call noop with the message "test successful".

2. Compile with gh aw v0.67.3: gh aw compile

3. Push and trigger via workflow_dispatch

4. The agent job starts, containers come up healthy, but the Copilot CLI exits with code 1 after ~5 seconds with no output

5. Recompile the same workflow with v0.67.1: works perfectly

Observed behavior (v0.67.3)

• pre_activation: success
• activation: success
• agent: failure — Copilot CLI exits with code 1, zero inference output
• detect_inference_access_error: false (token is valid)
• The CLI starts, health checks pass, then immediately exits:

[entrypoint] Unsetting sensitive tokens from parent shell environment...
[entrypoint] Unset COPILOT_GITHUB_TOKEN from /proc/1/environ
[SUCCESS] Containers stopped successfully
[WARN] Command completed with exit code: 1

Expected behavior

The Copilot CLI should run inference and execute the agent prompt, as it does with v0.67.1.

Environment

• Repository: elastic/docs-content-internal (private)
• gh-aw v0.67.3 (pre-release): fails
• gh-aw v0.67.1 (stable): works
• Failed run: https://github.com/elastic/docs-content-internal/actions/runs/24193615478
• Working run (v0.67.1): https://github.com/elastic/docs-content-internal/actions/runs/24193782877

Additional context

We also observed a possibly related issue: the MCP gateway v0.2.16 (used in v0.67.3 compiled lock files) filters out all tools when tools: ["*"] is set, keeping 0 of N tools. The v0.2.16 release notes say ["*"] should allow all tools, but the wildcard appears to be treated as a literal tool name. This was observed in a separate run: [allowed-tools] Filtered 6 tools from elastic-docs: keeping 0 of 6.</issue_description>

Comments on the Issue (you are @copilot in this section)

@pelikhan /plan open sub issue for the tool filtering issue in the gateway @pelikhan @copilot focus on diagnosing the copilot start issue