brew trust should use --tap instead of --formula in README #832

Problem

The README installation section currently recommends:

brew trust --formula gentleman-programming/tap/gentle-ai

This only trusts one formula. Users who later try to brew install other formulas from the same tap (e.g. engram, gga, gentle-creation) will hit the same Refusing to load formula from untrusted tap error.

Suggested Fix

Change to --tap so the entire tap is trusted at once:

brew trust --tap gentleman-programming/tap

This is a one-time command that covers all current and future formulas from the tap, which is the expected behavior for users who explicitly chose to add the tap.

Reproduction

1. Set HOMEBREW_REQUIRE_TAP_TRUST (Homebrew 6.0+)
2. brew tap Gentleman-Programming/homebrew-tap
3. brew trust --formula gentleman-programming/tap/gentle-ai
4. brew install gentle-ai → ✅ works
5. brew install gentleman-programming/tap/engram → ❌ Refusing to load formula from untrusted tap

Environment

• Homebrew 6.0.0
• HOMEBREW_REQUIRE_TAP_TRUST: set
• Linux (also affects macOS)