feat(web): templ partials replace the last UI twins (collections grid, conflicts list)

Both pages had a templ render (initial load) and a TypeScript twin
(innerHTML rebuild on refresh) of the same fragment. The twins are
deleted; the server-rendered markup is now the only markup.

- collections: the library switcher swaps in the new books-grid partial
  (GET /collections/:id/books-grid) instead of re-rendering cards from
  the /api/collections JSON. Book loading is extracted into
  Config.loadCollectionBooks, shared verbatim by the page and the
  partial (smart / dashboard-query / manual branches, family-lens
  scoping via resolveLibrary + UserVisibleLibraryIDs) so the two cannot
  drift.
- conflicts: resolve/dismiss refreshes swap the new list partial
  (GET /conflicts/list) with the stats bar as an out-of-band swap,
  instead of the TS twin — which rendered a degraded card (no
  checkboxes, no timestamps), pointed at a window.showResolveModal that
  does not exist, and updated stats via element ids the SSR never had.
- shims.d.ts: window.htmx typing (ajax/process) for TS callers.

Visibility note: the books-grid partial inherits its family-lens
scoping from the shared loader (identical to the detail page); a
dedicated hidden-library pin test for the partial route is still worth
adding in the next test pass.

templates/collections.templ

@@ -14,6 +14,76 @@ func pluralizeBooks(n int) string {
 	return "books"
 }
 
+// CollectionBooksGrid renders the content of #books-container: the
+// collection's book cards, or the empty state. Shared by the collection
+// detail page and the /collections/:id/books-grid partial route (the
+// library switcher refreshes the grid through it — rendering ownership:
+// templ renders, JS only swaps).
+templ CollectionBooksGrid(collection CollectionData, books []handlers.BookInfo) {
+					if len(books) == 0 {
+						<div id="empty-state" class="col-span-full card text-center py-16" style="color: var(--text-secondary)">No books in this collection yet.</div>
+					}
+					for _, book := range books {
+						<div class="card p-4 rounded-2xl collection-book-card" data-title={ book.Title } data-author={ book.Author } data-media-id={ book.MediaItemID }>
+							<div class="flex gap-4">
+								if !collection.IsSystem && !collection.IsSmart {
+									<div class="flex-shrink-0 pt-1">
+										<label class="flex items-center cursor-pointer p-2 -m-2">
+											<input
+												type="checkbox"
+												class="w-5 h-5"
+												:checked={ "selectedBooks.includes(" + JSONArg(book.MediaItemID) + ")" }
+												@change={ "toggleSelection(" + JSONArg(book.MediaItemID) + ")" }
+											/>
+										</label>
+									</div>
+								}
+								<div class="flex-1 min-w-0">
+									<a href={ "/media/" + book.MediaItemID }>
+										<h3 class="font-semibold text-lg mb-1 line-clamp-2 hover:underline" style="color: var(--text-primary)">
+											{ book.Title }
+										</h3>
+									</a>
+									if book.Author != "" {
+										<p class="text-sm line-clamp-1" style="color: var(--text-secondary)">
+											by { book.Author }
+										</p>
+									}
+								</div>
+								<div class="flex-shrink-0 w-16 sm:w-20">
+									<a href={ "/media/" + book.MediaItemID }>
+										if book.CoverImagePath != "" {
+											<img
+												src={ book.CoverImagePath }
+												alt="Cover"
+												class="w-full aspect-[3/4] object-cover rounded-lg shadow-md"
+												onerror="this.src='/static/placeholder-book.svg'"
+											/>
+										} else {
+											<img
+												src="/static/placeholder-book.svg"
+												alt="Cover"
+												class="w-full aspect-[3/4] object-cover rounded-lg shadow-md"
+											/>
+										}
+									</a>
+								</div>
+							</div>
+							if !collection.IsSystem && !collection.IsSmart {
+								<div class="mt-3 pt-3 border-t" style="border-color: var(--border);">
+									<button
+										@click={ "requestRemoveBook(" + JSONArg(book.MediaItemID) + ")" }
+										class="btn btn-secondary w-full"
+									>
+										@Icon("trash", "h-4 w-4")
+										<span>Remove from Collection</span>
+									</button>
+								</div>
+							}
+						</div>
+					}
+}
+
 templ Collection(user User, collections []CollectionData, errorMessage string) {
 	<!DOCTYPE html>
 	<html lang="en">
@@ -210,68 +280,7 @@ templ CollectionDetail(user User, collection CollectionData, books []handlers.Bo
 					</div>
 				</div>
 				<div id="books-container" class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-4 gap-6">
-					if len(books) == 0 {
-						<div id="empty-state" class="col-span-full card text-center py-16" style="color: var(--text-secondary)">No books in this collection yet.</div>
-					}
-					for _, book := range books {
-						<div class="card p-4 rounded-2xl collection-book-card" data-title={ book.Title } data-author={ book.Author } data-media-id={ book.MediaItemID }>
-							<div class="flex gap-4">
-								if !collection.IsSystem && !collection.IsSmart {
-									<div class="flex-shrink-0 pt-1">
-										<label class="flex items-center cursor-pointer p-2 -m-2">
-											<input
-												type="checkbox"
-												class="w-5 h-5"
-												:checked={ "selectedBooks.includes(" + JSONArg(book.MediaItemID) + ")" }
-												@change={ "toggleSelection(" + JSONArg(book.MediaItemID) + ")" }
-											/>
-										</label>
-									</div>
-								}
-								<div class="flex-1 min-w-0">
-									<a href={ "/media/" + book.MediaItemID }>
-										<h3 class="font-semibold text-lg mb-1 line-clamp-2 hover:underline" style="color: var(--text-primary)">
-											{ book.Title }
-										</h3>
-									</a>
-									if book.Author != "" {
-										<p class="text-sm line-clamp-1" style="color: var(--text-secondary)">
-											by { book.Author }
-										</p>
-									}
-								</div>
-								<div class="flex-shrink-0 w-16 sm:w-20">
-									<a href={ "/media/" + book.MediaItemID }>
-										if book.CoverImagePath != "" {
-											<img
-												src={ book.CoverImagePath }
-												alt="Cover"
-												class="w-full aspect-[3/4] object-cover rounded-lg shadow-md"
-												onerror="this.src='/static/placeholder-book.svg'"
-											/>
-										} else {
-											<img
-												src="/static/placeholder-book.svg"
-												alt="Cover"
-												class="w-full aspect-[3/4] object-cover rounded-lg shadow-md"
-											/>
-										}
-									</a>
-								</div>
-							</div>
-							if !collection.IsSystem && !collection.IsSmart {
-								<div class="mt-3 pt-3 border-t" style="border-color: var(--border);">
-									<button
-										@click={ "requestRemoveBook(" + JSONArg(book.MediaItemID) + ")" }
-										class="btn btn-secondary w-full"
-									>
-										@Icon("trash", "h-4 w-4")
-										<span>Remove from Collection</span>
-									</button>
-								</div>
-							}
-						</div>
-					}
+					@CollectionBooksGrid(collection, books)
 				</div>
 			</div>
 			if !collection.IsSystem && !collection.IsSmart {