feat: add Enterprise Copilot Agents Tab adventure path (step 11d)

[Copilot]

Adds a zero-install path for enterprise Copilot users: start an agent session from the GitHub UI, paste a prompt, get a PR with the compiled workflow — no gh-aw CLI required.

New file: workshop/11d-build-copilot-agents.md

• Agents tab entry point — how to open a session from the GitHub Copilot/Agents tab
• Copy-paste prompts for each scenario (A/B/C) — each prompt points the agent at https://github.com/github/gh-aw/blob/main/create.md to bootstrap format knowledge, then specifies the scenario requirements and asks for a compiled PR
• Session monitoring — activity feed phases (read → plan → write → compile → open PR)
• PR review and merge flow — what to verify in the diff (.md + .lock.yml), how to request revisions via PR comments, merge steps
• Post-merge note — how to get CLI access later or iterate via a follow-up agent session

Touchpoints in existing files

File	Change
workshop/README.md	Curriculum row for step 11d
workshop/00-welcome.md	"Enterprise Copilot user" row in the "Choose your path" table
workshop/10-choose-your-scenario.md	NOTE callout surfacing the enterprise path + step 11d added to "Next" navigation

No separate design step (10d): Adventures A–C have design steps because learners write the brief manually. Here the agent handles both design and build from the prompt.

[pelikhan]

@copilot this feature applies to GitHub Copilot users with the Agents tab enabled, not just enterprise.

[Copilot]

@copilot this feature applies to GitHub Copilot users with the Agents tab enabled, not just enterprise.

Fixed in the latest commit. "Enterprise Copilot" language has been removed throughout — the path is now described as available to any GitHub Copilot user with the Agents tab enabled, in 11d-build-copilot-agents.md, 00-welcome.md, 10-choose-your-scenario.md, and README.md.