refactor: centralize theme/config/utils + fix data and console bugs

Phase 1 of the cohesion refactor (behavior-preserving):

Single source of truth:
- New src/lib/theme.ts: category colors (moved from data.ts, re-exported
  for back-compat), derived hex strings, nebula palette, UI colors, CSS var map
- New src/lib/config.ts: breakpoint, zoom, parallax, node radii, particle
  counts, animation timings (previously scattered magic numbers)
- New src/lib/utils/tree.ts: getNodeById, getNodeRadius, getDistanceFromOrigin,
  getBeamIntensity (pure helpers lifted out of onMount)
- New src/lib/utils/stats.ts: branch ids/labels, proficiency order, and the
  stats-panel aggregation helpers (deduped from inline copies)
- SkillTree.svelte now imports all of the above; removed the duplicated
  getCategoryColorHex, stats helpers, branch id/label lists, and inline magic numbers
- Populated src/lib/index.ts barrel

Bug fixes:
- data.ts: tmdbAPI pypiUrl pointed at tvdbAPI -> corrected to tmdbAPI
- Removed/ gated stray console.log noise (skill-tree-loaded, SW logs)
- Removed dead vars (maxAlpha, glowMaxAlpha) and unused catch binding

Tooling: ESLint + Prettier now clean; added Vitest unit tests for the new
pure utils (14 tests). svelte-check: 0 errors. build: ok.

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

src/lib/utils/stats.ts

@@ -0,0 +1,82 @@
+// ==========================================================================
+// STATS UTILS — pure aggregation for the RPG-style character panel.
+// ==========================================================================
+
+import { treeNodes, type TreeNode } from '$lib/data';
+
+/** Skill branch ids and their display labels (single source of truth). */
+export const BRANCH_IDS = [
+	'concepts',
+	'tools-devops',
+	'frontend',
+	'backend-real-time',
+	'languages'
+] as const;
+
+export const BRANCH_LABELS: Record<string, string> = {
+	concepts: 'Concepts',
+	'tools-devops': 'Tools & DevOps',
+	frontend: 'Frontend',
+	'backend-real-time': 'Backend & Real-Time',
+	languages: 'Languages'
+};
+
+/** Proficiency sort order (best first). */
+export const PROFICIENCY_ORDER: Record<string, number> = {
+	expert: 0,
+	advanced: 1,
+	intermediate: 2,
+	beginner: 3
+};
+
+/** Character "level" derived from years since the first job started. */
+export function calculatePlayerLevel(): number {
+	const earliestStart = new Date('2020-10-01'); // First job
+	const now = new Date();
+	const millisPerYear = 1000 * 60 * 60 * 24 * 365.25;
+	const years = (now.getTime() - earliestStart.getTime()) / millisPerYear;
+	return Math.floor(years);
+}
+
+/** Character "class" — the origin node's job title. */
+export function getPlayerClass(): string {
+	const originNode = treeNodes.find((node) => node.id === 'origin');
+	return originNode?.jobTitle || 'Software Engineer';
+}
+
+/** Group skill nodes by branch, sorted by proficiency. */
+export function aggregateSkills(): Record<string, { label: string; skills: TreeNode[] }> {
+	const result: Record<string, { label: string; skills: TreeNode[] }> = {};
+
+	BRANCH_IDS.forEach((branchId) => {
+		const skills = treeNodes.filter(
+			(node) => node.parentId === branchId && node.category === 'skills'
+		);
+
+		skills.sort((a, b) => {
+			const aOrder = PROFICIENCY_ORDER[a.proficiency || 'beginner'];
+			const bOrder = PROFICIENCY_ORDER[b.proficiency || 'beginner'];
+			return aOrder - bOrder;
+		});
+
+		result[branchId] = { label: BRANCH_LABELS[branchId], skills };
+	});
+
+	return result;
+}
+
+/** Count all skill nodes by proficiency tier. */
+export function countByProficiency(): {
+	expert: number;
+	advanced: number;
+	intermediate: number;
+	beginner: number;
+} {
+	const counts = { expert: 0, advanced: 0, intermediate: 0, beginner: 0 };
+	treeNodes.forEach((node) => {
+		if (node.proficiency) {
+			counts[node.proficiency]++;
+		}
+	});
+	return counts;
+}