Add browser/CCA compile fallback to Step 12 iteration flow

[Copilot]

workshop/12-test-and-iterate.md had a high rate of workflow-not-compiled failures because the step required gh aw compile but did not provide a non-terminal path for CCA/mobile learners. This update preserves the mandatory compile requirement while adding a verifiable browser-first path.

• What changed

  • Added a new “If You Cannot Run the Terminal” section in Step 12 with explicit CCA/mobile guidance.
  • Added a concrete Copilot prompt instructing learners to run gh aw compile and commit both the workflow source and regenerated lock file.
  • Linked to the existing browser-first iteration path in side-quest-12-01-iterate-agent-output.md.

• Checkpoint hardening

  • Added a checkpoint item requiring browser/Copilot-agent learners to confirm the latest commit updated the corresponding .lock.yml file.

• Learner path impact

  • Keeps the existing IMPORTANT compile callout and compile-before-test contract intact.
  • Improves scaffolding for learners who cannot execute terminal commands directly.

Please run `gh aw compile` and commit both the workflow `.md` file and the regenerated `.lock.yml` file.

• Fixes [workshop-sim] Improve: Add CCA/browser compile path to test-and-iterate step #1657

[pelikhan]

@copilot teach to use the /agentic-workflows skill