Stop rebuilding the defaults Hash on every option read

[tas50]

Summary

Every one of the 13 generated option readers ran:

options[option] || options[option.to_s] || default_options[option]

So each read that was not explicitly set allocated a String from to_s and then built a fresh 5-entry Hash — including an ENV lookup — just to pull one key back out of it. Options#for_ps1? reads two options, so it did that twice per call, and for_ps1? is on the hot path for both script generation and artifact filtering.

This freezes the String key once when the reader is defined, and looks up a single default instead of materializing the whole Hash.

license_id still reads ENV["CHEF_LICENSE_KEY"] on every access, so environment changes are picked up exactly as before.

The || chain is deliberately kept rather than switched to nil? checks, so an explicitly false option still falls through to its default exactly as it does today.

Measurements

Ruby 4.0.6:

	before	after	speedup	allocations
#shell_type (default)	445 ns	180 ns	2.5x	3.02 → 0.02
#product_version (default)	450 ns	140 ns	3.2x	3 → 0
#for_ps1?	907 ns	327 ns	2.8x	7 → 1
#latest_version?	483 ns	174 ns	2.8x
.new	4094 ns	2632 ns	1.6x	30 → 16
#validate_options!	1193 ns	867 ns	1.4x

#product_name and other explicitly-set reads are unchanged at ~78 ns, as expected — they never reached the defaults branch.

Verification

• 576 unit examples and the functional spec pass; chefstyle clean.
• Explicit assertions that defaults, explicitly-set values, String-keyed options, nil options and the CHEF_LICENSE_KEY environment fallback all resolve identically, including picking up an environment change between two Options.new calls.
• All 176 golden SHA256 digests match main.