feat: curated font pairings library

[jubscodes]

Split from #36.

Problem

Default font choices (system fonts, generic sans-serif) are one of the biggest tells that something was AI-generated. The current system doesn't push users toward distinctive font choices.

Proposal

Build a reference of proven font pairings organized by personality/mood:

• Editorial: Playfair Display + Source Sans Pro
• Technical: JetBrains Mono + Inter
• Luxury: Cormorant Garamond + Montserrat
• Playful: Fraunces + DM Sans
• (10+ pairings total)

Each pairing includes: heading font, body font, mono font, recommended weights, sample CSS, and which brand archetypes it suits.

Acceptance criteria

• Font pairings reference (location TBD — likely `gsp-typography/pairings.md` or sibling)
• 10+ curated combinations
• Each pairing tagged with personality/archetype fit
• Pairings discoverable from `/gsp-typography` and `/gsp-typescale` skills

Related

• feat: premium typography — curated font pairings and personality matching #36 — original typography umbrella (closed when split)