Apply frozen string literals and constant extraction to high-frequency knife commands

[nikhil2611]

Epic

Part of Crawl Track backlog epic.

Background

Ex6 (Performance) added PARTIAL_SEARCH_FIELDS as a frozen constant in knife status. The same pattern (frozen string literals, extracted field arrays) should be applied to the highest-frequency commands to reduce GC pressure in large Chef environments.

Code Paths

• lib/chef/knife/status.rb:37 — PARTIAL_SEARCH_FIELDS reference implementation
• lib/chef/knife/search.rb — repeated string construction in #run
• lib/chef/knife/node_list.rb — inline string arrays per invocation
• lib/chef/knife/cookbook_list.rb — similar pattern

Acceptance Criteria

• # frozen_string_literal: true magic comment added to at least 3 commands
• Repeated literal arrays/hashes extracted to named frozen constants
• bundle exec rake spec passes with 0 failures after changes
• No behavior change — pure refactor

Dependencies

• Depends on: Ex6 performance pattern (already merged)
• Depends on: Issue Raise test line coverage from 47% to 70%+ #116 (coverage) — higher coverage makes this refactor safer
• Blocks: nothing

Estimated Size

Small–Medium