Extract hardcoded trial count into NUM_TRIALS constant set to 7, collect all timing results into a list, and add graph_results function that prints a horizontal ASCII bar chart scaling each run's times relative to the global maximum across all benchmarks and languages.
Add a benchmark runner script (benchmark/run_all) that executes multiple
fibonacci implementations across languages (Lua, Python, Ruby, Wren) and
computes mean, median, and standard deviation from 7 runs. Update existing
fib benchmarks to loop 5 times at fib(30) with elapsed timing. Introduce
OS.clock primitive in C core and OS class to support timing in Wren.
Adjust number formatting to "%.14g" for consistent output precision.
