Run independent factory issues concurrently with bounded developer lanes

The current recipe stops development whenever any PR awaits review, so an independent backlog still runs one issue at a time.

Ready for dev.

Acceptance criteria:

• Run two or more developer lanes using the existing Automation Service scheduling/concurrency controls and the canonical issue-to-PR workflow.
• Give each lane deterministic, disjoint issue ownership; do not start duplicate implementations or change ownership while runs are active.
• Respect explicit issue dependencies before development and keep the number of open implementations bounded.
• Use GitHub's existing branch-update operation to refresh stale PR bases and require independent acceptance of the new head.
• Preserve identical behavior in local/Docker workspaces and per-role gateway/profile secret boundaries.
• Verify overlapping development and independent review in the software factory demonstration under a bounded machine resource budget.

Start by tracing the existing recipe and the Automation Service scheduling and concurrency controls, then inspect the canonical issue-to-PR workflow. Done means the acceptance criteria are demonstrated with deterministic lane ownership, dependency and implementation bounds, branch updates, preserved workspace and secret behavior, and overlapping development and review within the stated resource budget.