refactor(storybook): remove unused SW header demo stories

Remove nine SW/Header demo pages (property-fields, property-shape-slot,
composition, colorize, dynamic-controls, property-bar, additional-hover,
property-panel, layer-detail-input) and the demo code and Storybook-only
CSS used only by them. SW Stories 19 -> 10, total 338 -> 329.

The package runtime, public API, AI template and the retained Stories
(Overview, Dropdown, Property Panel 4-state comparison, Window Move
Motion and others) are unchanged. Add a current regression script and
mark the older scripts that open the retired IDs as historical evidence.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/sw/tests/property-panel-comparison.browser.mjs

@@ -1,3 +1,5 @@
+// Historical since 2026-10-19: opens SW Story IDs retired by the unused demo removal (property-panel and four others in verify). Kept as evidence
+// for its recorded run; current regression: storybook-unused-removal.browser.mjs.
 import { createRequire } from 'node:module'
 import { mkdir, readFile, writeFile } from 'node:fs/promises'
 import path from 'node:path'