fix(types): clear web/src type and lint debt with real types

tsc --noEmit and oxlint web/src are now both clean; vp check passes.

- htmx: one canonical Htmx interface in shims.d.ts (ajax/process/trigger
  per the htmx 2.x API). alpine.ts had a second, conflicting Window.htmx
  declaration (TS2717) — removed; bookPicker/collections lose their
  (window as any) escapes now that Window.htmx is properly typed.
- tsconfig lib ES2020 -> ES2021 + DOM.Iterable: replaceAll exists
  (escapeHtml) and for..of over querySelectorAll results is legal.
  Type-checking only — vite emits at esnext regardless.
- custom-section-builder: selectedBooks holds identity fields only;
  typed as Pick<BookInfo, ...> instead of forcing partial API shapes.
  The API-critical BookInfo contract is untouched.
- toast: real bug found by the type system — setup.ts passes 'warning'
  but getToastConfig had no entry, so the warning toast threw TypeError
  at runtime instead of displaying. Added the type + config. Uses
  bg-yellow-500 (verified present in scanned templates => generated by
  Tailwind); the one intentional behavior change in this commit.
- book-detail: instanceof narrowing replaces an as-cast; unused
  AnnotationSource import removed.
- password_validation: explicit HTMLElement | null for the checklist
  list (querySelector('ul') infers HTMLUListElement, conflicting with
  the container-as-list branch).
- stats: tooltip parsed value typed via annotation (bar=scalar,
  line={x,y}); dead getActiveRange() removed (was already tree-shaken
  out of every bundle).
- library-switcher: onSwitch honestly typed void | Promise<void>
  (series.ts passes a sync navigator).
- 20 unused catch bindings converted to optional catch binding.

Verification: fresh build is byte-reproducible; every chunk is
identical to the pre-fix build except main.js (instanceof narrowing,
regex fix, stats refactor), reader.js (destructure), and the shared
storage chunk (renamed — carries toast.ts). reader/main diffs audited
hunk-by-hunk against the intended edits.

web/src/library-switcher.ts

@@ -73,7 +73,9 @@ export async function switchWithTransition(
 }
 
 export interface LibrarySwitcherOptions {
-  onSwitch: (libraryId: string) => Promise<void>;
+  // Async switchers (SSR navigation awaits nothing, API-backed switchers
+  // await their fetch) — hence void | Promise<void>.
+  onSwitch: (libraryId: string) => void | Promise<void>;
 }
 
 export function initLibrarySwitcher(options: LibrarySwitcherOptions): void {