docs: gaze --test-short flag and coverage behavior change

[yvonnedevlinrh]

Context

PR unbound-force/gaze#194 removes the hardcoded -short flag from coverage generation and adds an opt-in --test-short CLI flag.

What changed

• Behavioral change: -short is no longer passed to go test -coverprofile by default — all tests now contribute to coverage
• New --test-short CLI flag on gaze crap, gaze report, and gaze self-check (default: false)
• GAZE_COVERAGE_RUN=1 env var added to prevent infinite recursion in gaze self-check
• CRAP scores may change after upgrade without any user action (more tests → different coverage numbers)

What needs updating

• Add --test-short to the CLI flags table for gaze crap, gaze report, gaze self-check
• Add a migration note: coverage now reflects the full test suite by default; users who relied on implicit -short for speed must now pass --test-short explicitly
• Note that CRAP scores may change after upgrading (silent behavioral change)

Affected pages

• content/docs/projects/gaze.md — CLI flags table
• Any page discussing CRAP score calculation or coverage methodology