refactor(import): add v4section/v4url aliases, inline clamp wrappers, replace classes with fns

Finding 5: Introduce V4Url + V4Section<T> type aliases in reactive-resume-v4-json.tsx; collapse
310-line V4ResumeData type (13x 5-field section header, 11x {label,href}) into typed aliases.
Inferred shape is structurally identical.

Finding 6: Remove 9 single-caller clamp/pxToPt wrappers; replace compile-time constants
(rotation=0, sidebarWidth=35, shadowWidth=0, gapX=4, gapY=6) with literals; inline dynamic
calls (clamp(x, 32, 512) etc.) at the two body/heading typography call sites.

Finding 7: Convert three stateless single-method importer classes to plain functions.
Extract shared rethrowAsImportError() to error.ts, replacing triplicated ZodError catch blocks.
Update web import dialog + all in-package test files to use function API.

Claude-Session: https://claude.ai/code/session_012Bnvt1MghwHj4qQRxuQUGa

packages/import/src/reactive-resume-json.tsx

@@ -1,6 +1,7 @@
 import type { ResumeData } from "@reactive-resume/schema/resume/data";
-import { flattenError, ZodError } from "zod";
+import { ZodError } from "zod";
 import { resumeDataSchema, sectionTypeSchema } from "@reactive-resume/schema/resume/data";
+import { rethrowAsImportError } from "./error";
 
 const BUILT_IN_LAYOUT_SECTION_IDS = sectionTypeSchema.options.filter((section) => section !== "cover-letter");
 
@@ -62,18 +63,13 @@ function normalizeBuiltInSectionsInLayout(data: ResumeData): ResumeData {
 	};
 }
 
-export class ReactiveResumeJSONImporter {
-	parse(json: string): ResumeData {
-		try {
-			const parsed = resumeDataSchema.parse(JSON.parse(json));
-			return resumeDataSchema.parse(normalizeBuiltInSectionsInLayout(parsed));
-		} catch (error) {
-			if (error instanceof ZodError) {
-				const errors = flattenError(error);
-				throw new Error(JSON.stringify(errors));
-			}
-
-			throw error;
-		}
+// ponytail: stateless single-method class → plain function
+export function parseReactiveResumeJSON(json: string): ResumeData {
+	try {
+		const parsed = resumeDataSchema.parse(JSON.parse(json));
+		return resumeDataSchema.parse(normalizeBuiltInSectionsInLayout(parsed));
+	} catch (error) {
+		if (error instanceof ZodError) rethrowAsImportError(error);
+		throw error;
 	}
 }