Fix --timeout to accept s/ms suffix for user convenience

[a2Fsa2k]

Summary

The --timeout option previously rejected values with a trailing s or
ms suffix (e.g. --timeout 5s) because strtod_strict() validates
that no trailing characters remain after the number.

This change strips recognized time unit suffixes (s for seconds,
ms for milliseconds) from the argument before parsing, so users can
write more natural forms like --timeout 5s instead of --timeout 500.

Changes

• Modified the -t / --timeout case handler in src/fping.c to
  detect and strip trailing s or ms suffix
• The multiplier is adjusted accordingly: s suffix uses 1,000,000
  (seconds to microseconds), ms suffix uses 1,000 (milliseconds to
  microseconds)
• Backward compatible: bare numeric values without suffix continue to
  work as before

Test plan

• fping --timeout 5s localhost → alive
• fping --timeout 500ms localhost → alive
• fping --timeout 5 localhost → alive (backward compat)
• fping --timeout 5x localhost → usage error (invalid suffix rejected)

[gemini-code-assist]

Code Review

This pull request adds support for 'ms' and 's' suffixes to the timeout option (-t) in fping.c. However, a critical bug was identified where the timeout multipliers are off by a factor of 1000 because opt_timeout is internally represented in nanoseconds rather than microseconds. Correcting these multipliers is necessary to prevent premature timeouts on remote hosts.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[a2Fsa2k]

Good catch — opt_timeout is in nanoseconds (added to current_time_ns at line 2016). Fixed the multipliers in the amended commit: seconds now multiply by 1e9, milliseconds by 1e6.