feat(ci): add progress output and job summary to e2e action

[hanthor]

Summary

Two improvements to make e2e failures easier to diagnose without downloading artifacts:

1. Live progress output in CI log

Adds --format progress to the behave command. Previously all formatters wrote to files, leaving the CI log nearly empty during the test run. Now the log shows live dot-notation as tests execute:

SSSSS.SSSS.F.SSS...

(S = skipped, . = passed, F = failed)

2. GitHub Actions job summary

Adds a "Summarise results" step (if: always()) that runs on the GitHub Actions runner after tests complete. It:

• Prints a compact failure digest to the CI log with the exact scenario, step name, and error:

================================================================
E2E FAILED: 51 passed / 2 failed / 29 skipped (total 82)

Failed scenarios:
  ❌  [GNOME app launch smoke tests] Files file manager launches successfully
       step : the Files file manager launches successfully
       error: ASSERT FAILED: Visible Files window not found. Visible frames: []
  ❌  [System health smoke checks] No failed systemd units at boot
       step : No failed systemd units at boot
       error: ASSERT FAILED: Failed systemd units detected: ['fwupd-refresh.service ...']
================================================================

• Writes a GitHub Actions job summary (markdown table) visible directly in the Actions UI:

✅ Passed	❌ Failed	⏭️ Skipped	Total
51	2	29	82

With a failures table showing Feature / Scenario / Failed Step / Error, and an SLA violations table.

No artifact download needed to see what broke.

Verified against real artifacts from run 26737615278.