feat(temas): live theme builder in /temas/color (deriveScheme end-to-end)

Seed color + variant (tonal/vibrant/monochrome) -> deriveScheme -> generateScale
-> live preview of the 5 hierarchy role scales (12 steps each, step 9 ringed) +
their APCA on-solid chips. The full uix.color builder pipeline, reactive and
pure. Verified in-browser: blue seed -> tertiary purple (+60deg), monochrome
collapses to one gray, primary = seed verbatim.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/routes/temas/color/+page.svelte

@@ -32,7 +32,20 @@
 		type ColorRole
 	} from '$uix/eidos/lib/config-types'
 	import { INTENTS } from '$uix/intent'
-	import { apcaLc, oklchToGammaRgb, parseColor, wcagContrastRatio } from '$color'
+	import {
+		apcaLc,
+		deriveScheme,
+		generateScale,
+		oklchToGammaRgb,
+		oklchToHex,
+		parseColor,
+		pickNearestTemplate,
+		pickOnSolid,
+		scaleToTemplate,
+		wcagContrastRatio,
+		type ScaleSteps,
+		type SchemeVariant
+	} from '$color'
 
 	let theme = $state<'light' | 'dark'>('light')
 
@@ -77,6 +90,41 @@
 	const SURFACES = ['default', 'raised', 'overlay', 'muted'] as const
 	const CONTENTS = ['primary', 'secondary', 'muted', 'disabled'] as const
 	const BORDERS = ['subtle', 'default', 'strong'] as const
+
+	// ── Theme builder (deriveScheme + generateScale, live) ────────────────────
+	// Curve donors for the generator: the base light scales as OKLCH templates.
+	const TEMPLATES: Record<string, ScaleSteps> = Object.fromEntries(
+		Object.entries(THEME_BASE_LIGHT_COLOR_SCALES).map(([name, scale]) => [
+			name,
+			scaleToTemplate(STEPS.map((s) => scale[s]))
+		])
+	)
+	const BUILDER_VARIANTS = ['tonal', 'vibrant', 'monochrome'] as const satisfies readonly SchemeVariant[]
+
+	let seedHex = $state('#8e4ec6')
+	let builderVariant = $state<SchemeVariant>('tonal')
+
+	interface BuilderRole {
+		role: string
+		steps: string[]
+		solidHex: string
+		onSolid: string
+	}
+	const builderRoles = $derived.by((): BuilderRole[] => {
+		let seed: ReturnType<typeof parseColor>
+		try {
+			seed = parseColor(seedHex)
+		} catch {
+			return []
+		}
+		const scheme = deriveScheme(seed, builderVariant)
+		return Object.entries(scheme).map(([role, roleSeed]) => {
+			const tpl = TEMPLATES[pickNearestTemplate(roleSeed, TEMPLATES)]
+			const steps = generateScale(roleSeed, tpl).map(oklchToHex)
+			const pick = pickOnSolid(roleSeed, { onSolid: '#ffffff', onSolidContrast: '#1c1917' }, 60)
+			return { role, steps, solidHex: steps[8], onSolid: oklchToHex(pick.color) }
+		})
+	})
 </script>
 
 <svelte:head>
@@ -119,6 +167,63 @@
 			activas, así que cambia con el tema.
 		</p>
 
+		<!-- Theme builder — deriveScheme + generateScale, live -->
+		<section class="preset">
+			<div class="head">
+				<span class="eyebrow">uix.color · deriveScheme + generateScale</span>
+				<h2>Theme builder <small>(1 color → esquema completo · en vivo)</small></h2>
+				<p>
+					Elige un color de marca y una variante: el motor <strong>deriva</strong> los roles de
+					jerarquía (fórmula de Material 3 en OKLCH) y <strong>genera</strong> cada escala de 12 pasos
+					con su pick on-solid (APCA). Los 6 intents NO se derivan (canon del libro). Es el theme
+					builder de punta a punta — en runtime se aplicaría con <code>setCssVariables</code>.
+				</p>
+			</div>
+			<div class="builder-controls">
+				<label class="builder-seed">
+					semilla
+					<input type="color" bind:value={seedHex} />
+					<code>{seedHex}</code>
+				</label>
+				<div class="seg" role="group" aria-label="Variante">
+					{#each BUILDER_VARIANTS as v}
+						<button
+							type="button"
+							data-active={builderVariant === v}
+							onclick={() => (builderVariant = v)}
+						>
+							{v}
+						</button>
+					{/each}
+				</div>
+			</div>
+			<div class="builder-out">
+				{#each builderRoles as r}
+					<div class="role-row">
+						<span class="role-name"><strong>{r.role}</strong></span>
+						<div class="swatches">
+							{#each r.steps as hex, i}
+								<span
+									class="sw"
+									class:nine={i === 8}
+									style="background: {hex}"
+									title="{r.role} {i + 1}"
+								></span>
+							{/each}
+						</div>
+					</div>
+				{/each}
+			</div>
+			<div class="builder-chips">
+				{#each builderRoles as r}
+					<div class="chip" style="background: {r.solidHex}; color: {r.onSolid}">
+						<strong>{r.role}</strong>
+						<small>{r.solidHex}</small>
+					</div>
+				{/each}
+			</div>
+		</section>
+
 		<!-- La paleta — 31 escalas × 12 pasos -->
 		<section class="preset">
 			<div class="head">
@@ -593,4 +698,38 @@
 		font-size: var(--font-size-xs);
 		color: var(--color-content-secondary);
 	}
+
+	/* Theme builder */
+	.builder-controls {
+		display: flex;
+		flex-wrap: wrap;
+		align-items: center;
+		gap: var(--space-4);
+	}
+	.builder-seed {
+		display: inline-flex;
+		align-items: center;
+		gap: var(--space-2);
+		font-size: var(--font-size-sm);
+		color: var(--color-content-secondary);
+	}
+	.builder-seed input[type='color'] {
+		inline-size: 44px;
+		block-size: 30px;
+		padding: 0;
+		border: 1px solid var(--color-border-default);
+		border-radius: var(--radius-sm);
+		background: none;
+		cursor: pointer;
+	}
+	.builder-out {
+		display: flex;
+		flex-direction: column;
+		gap: var(--space-2);
+	}
+	.builder-chips {
+		display: flex;
+		flex-wrap: wrap;
+		gap: var(--space-2);
+	}
 </style>