Fail fast when demo services exit

[imran-siddique]

What changed

• Readiness loops now detect child processes that exit before binding their port
• Error messages include the exit code and point to launcher logs
• The top-level runner bounds each demo to 180 seconds
• Applies the behavior consistently to demos 1, 2, 4, 5, 10 and the web console

Root cause

The launchers only polled a TCP port. If a child failed during startup, users waited the full readiness timeout with no indication that the process had already exited.

Validation

• Compiled every changed Python file
• Reproduced an immediate cMCP startup failure
• Confirmed failure returned in about 10 seconds with the child exit code
• Confirmed no demo server process remained
• Ran git diff --check