Islo run surfaces

Surfaces show live web interfaces and persistent terminal sessions in the line-run canvas. Read Surface usage for commands, readiness checks, and safety rules.

Ground rules:

• Use the installed islo surface --help output as the source of truth for supported kinds and flags.
• Only a stage agent with the line-run Surface environment invokes islo surface.
• A Line Manager routes a Surface request to the stage agent that owns the sandbox.