feat(filters+nav): author navigation end-to-end — arrays on every media response, deep-linkable bookshelf filters, clickable authors

Completes the A2c acceptance scenario: click an author on a book
detail page -> land on the bookshelf filtered to everything that
author wrote (including their share of co-authored books).

- Media detail + unscoped list resolved maps expose subtitle,
  explicit, authors, publishers (the library-scoped raw branch and
  the search endpoint already did — raw rows follow the SELECT).
- SearchMediaItemsUnified SELECT carries the new columns; the search
  endpoint serializes the row directly, so clients get them there too.
- book_detail.templ renders each author as a link to
  /bookshelf?author_filter=<name>.
- Bookshelf honors filter params in the URL on load (author_filter,
  series_filter, genre_filter, publisher_filter, tags_filter,
  narrator_filter, language_filter): pre-fills the form, applies it to
  the first grid load. Comma-joined values are multi-select via the
  server-side string_to_array split. Filtered views are shareable.

Pins widened: search rows (+7 keys), resolved keys (+4); changelog
entries in docs/contract_pins.md. Android follow-up plan written to
~/.opencode/plan/bookhoard-app-v2-compat.md.

web/src/bookshelf.ts

@@ -456,28 +456,66 @@ Alpine.data("bookshelf", () => ({
 }));
 
 // Standalone function - initialize the bookshelf (NOT async, like dashboard.ts)
+// A2c §5.3: deep-linkable filters. Reads known filter params from the URL
+// into the form inputs; returns true when at least one was applied. A
+// comma-joined value is a multi-select (the server splits it per element).
+function applyURLFilters(filterForm: HTMLFormElement | null): boolean {
+  if (!filterForm) return false;
+  const params = new URLSearchParams(window.location.search);
+  const filterNames = [
+    "author_filter",
+    "series_filter",
+    "genre_filter",
+    "publisher_filter",
+    "tags_filter",
+    "narrator_filter",
+    "language_filter",
+  ];
+  let applied = false;
+  for (const name of filterNames) {
+    const value = params.get(name);
+    if (!value) continue;
+    const input = filterForm.querySelector(
+      `[name="${name}"]`,
+    ) as HTMLInputElement | null;
+    if (input) {
+      input.value = value;
+      applied = true;
+    }
+  }
+  return applied;
+}
+
 function initBookshelf(): void {
+  const filterForm = document.getElementById(
+    "filter-form",
+  ) as HTMLFormElement;
+
+  // A2c §5.3: deep-linkable filters — /bookshelf?author_filter=Sapkowski
+  // pre-fills the form and applies it to the first grid load. Author
+  // links on the detail page (and anything else) can share filtered
+  // views; a comma-joined value is a multi-select (server splits it).
+  const urlApplied = applyURLFilters(filterForm);
+
   // Check if books were already rendered server-side
   const booksGrid = document.getElementById("books-grid");
   const hasServerBooks =
     booksGrid && booksGrid.querySelector("[data-book-id]") !== null;
 
-  if (!hasServerBooks) {
-    // Only trigger HTMX if no SSR books rendered
+  if (!hasServerBooks || urlApplied) {
     const librarySelect = document.getElementById(
       "library-select",
     ) as HTMLSelectElement;
     librarySelect?.addEventListener("change", () => {
       localStorage.setItem("selectedLibrary", librarySelect.value);
     });
-    if (librarySelect && librarySelect.value) {
-      const filterForm = document.getElementById(
-        "filter-form",
-      ) as HTMLFormElement;
-      if (filterForm) {
-        // Trigger initial HTMX load
-        window.htmx.trigger(librarySelect, "change");
-      }
+    if (urlApplied && filterForm) {
+      // A URL filter replaces the grid with the filtered set — the form
+      // submit serializes the library select too (it lives in the form).
+      window.htmx.trigger(filterForm, "submit");
+    } else if (librarySelect && librarySelect.value && filterForm) {
+      // Normal unfiltered initial HTMX load
+      window.htmx.trigger(librarySelect, "change");
     }
   }
   // Setup listener for HTMX swap events on the filters list