feat(roots): iOS/Swift token export + thoughtstream brand (River Mist)

[mattmaynes]

Adds two things to @rogueoak/roots, per spec 0032:

1. thoughtstream brand (River Mist)

The first REAL Canopy brand (vs the sunset demo), authored as DTCG token files at
packages/roots/examples/thoughtstream/, mirroring examples/sunset/ structure and role set.

River Mist is a calm slate-teal water palette:

• slate (primary): slate-600 #42666f light / slate-300 #8fb6bb dark
• mist (neutral): mist-50 #f3f6f6 (bg light), mist-900 #1e3238 (text light), mist-950 #0e1618 (bg dark)
• current (secondary teal), tide (accent aqua), plus cool-tuned status ramps

It maps all 39 Canopy semantic roles in light + dark and builds AA-clean through
buildBrand(): every role/state pair meets WCAG AA in both themes, each dark override differs from
its light value. (The surface primitive is named canvas to dodge a DTCG group/token path collision
with the color.surface role.)

2. iOS / Swift token export

swift.mjs / buildSwift() (exported at @rogueoak/roots/swift, bin roots-swift) generates one
Tokens.swift for a brand from the same config roots-brand reads - the native Swift target the
architecture always anticipated ("just another Style Dictionary platform - no token rewrite"). It
reuses the core transforms rather than re-resolving tokens by hand:

• Colours: two throwaway Style Dictionary instances resolve the brand's light + dark semantics to
  concrete hex (outputReferences: false), emitted as one Color(light:dark:) per role that adapts
  to the color scheme via a generated dynamic-UIColor initializer.
• Non-colours: a third instance resolves Canopy's OWN spacing / radius / type scale (shared
  across brands) to CGFloat points + Font helpers. rem -> points at 16pt/rem; a raw px pill
  (radius.full) is kept as-is.

Output is three caseless enums (CanopyColor / CanopySpacing / CanopyRadius / CanopyFont - the
idiomatic Swift namespace with no instances) with a "Do not edit - generated by Style Dictionary"
header. Generated on demand (not part of the web pnpm build), landing at
dist/<brand>/Tokens.swift.

Regenerate: npx roots-swift examples/thoughtstream/brand.config.json

Text("Thought Stream")
    .font(CanopyFont.sizeX2xlFont())
    .foregroundStyle(CanopyColor.text)
    .padding(CanopySpacing.x4)                 // 16pt
    .clipShape(RoundedRectangle(cornerRadius: CanopyRadius.md))  // 8pt

Verification

• node cli.mjs examples/thoughtstream/brand.config.json builds AA-clean (39/39 roles mapped).
• swiftc -typecheck passes on the generated Tokens.swift (real, compilable SwiftUI).
• Vitest: thoughtstream builds AA-clean; the Swift emitter's structure is asserted (header, primary
  light+dark hex, spacing/radius/font constants, CLI). pnpm test + pnpm lint green in roots, and
  the full monorepo pnpm build / test / lint are green.
• README + docs/overview/ (features, architecture) updated to match.

🤖 Generated with Claude Code