fix(system): validate launcher and timeit integer arguments

[belowzeroff]

What changes for users

Malformed numeric startup arguments are rejected instead of being silently truncated or overflowing: -c/--cores, -t/--timeit, and -Q/--querylog now require complete, range-checked integer values. Invalid values fail startup with a non-zero status before the runtime starts.

The same strict parsing is used by .sys.args, .sys.timeit, and .sys.cmd "timeit ...", so values such as 2abc, overflowing core counts, and 1.5 now return an error instead of changing runtime state unexpectedly.

Validation

• clean full test build with strict warnings
• 3924/3924 core tests passed
• release build passed with -Werror
• targeted runtime and Rayfall system coverage included

All checks pass.