feat(tokens): opt-in colour ladders and a semantic token layer

[drewstone]

The colour system from the Tangle Agents redesign, at its source.
Builder (agents.tangle.tools) already ships byte-identical copies of these two files ahead of this release (tangle-network/agent-builder#438); once Builder installs a brand with them, it imports these and deletes its copies.

What changes

• styles/ladders.css: 12 ramps × 12 steps, light and dark, from Radix Colors 3.0.0. Mauve is the neutral, iris the brand, green/amber/red/blue carry status, and plum, orange, grass, bronze, crimson and olive are domain ramps. Role aliases (--gray-*, --accent-*, --success-*, --warning-*, --danger-*, --info-*) and [data-domain] → --domain-1..12.
• styles/system.css: every tokens.css family (hsl, md3, depth, bg, text, border, surface, status, btn, sidebar) mapped to a ladder step, plus semantic tokens (--bg-page, --line, --fg-muted, --accent-text, --ink), role radii, type roles, motion and a three-level shadow scale.
• scripts/gen-ladders.mjs + radix-ramps.json generate both files (pnpm --filter @tangle-network/brand gen:ladders).
• Package exports for both files, a README section and a minor changeset.

Why opt in, not a remap of tokens.css
system.css turns light pages white and changes every token an app reads. Importing it is a per-app decision, so no other Tangle app changes when this releases.

Contrast, measured in the browser on Builder

• Light status chips use step 12 text: step 11 on step 3 is 4.21–4.25:1.
• --accent-text (iris 11): 6.07:1 on white, 8.33:1 on dark step 2.
• --line-field (mauve 9): 3.30:1 on white, 3.45:1 on dark step 2.
• --domain-bubble (light step 11): 4.51–6.07:1 with white text across the nine domain ramps.

Checked: pnpm test (374 passed), pnpm --filter @tangle-network/brand build, and the generator output diffed byte-for-byte against Builder's shipped copies.

[changeset-bot]

🦋 Changeset detected

Latest commit: 74a994d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@tangle-network/brand	Minor

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[tangletools]

✅ Auto-approved drewstone PR — 74a994db

This PR was opened by the trusted drewstone account.
No automated review runs on this PR. This approval rests on the rule above alone.

_{tangletools · auto-approval · reason: drewstone_author · 2026-09-24T02:14:28Z}