fix(ui): user-test round 4 — five browser-reported control defects

Every one of these was silent at the code level and loud in a real
browser; each fix carries its own tripwire (render pin, unit pin, or
CSP-safe rewrite) so the class cannot quietly return.

1. Theme picker dead since the CSP migration (eb57b720): the Appearance
   panel's theme buttons emitted `@click="selectTheme(opt.Name)"` as
   LITERAL text (templ gotcha #1 — quoted attribute values are never
   interpolated; `opt` is a Go loop var), so Alpine threw "Undefined
   variable: opt" on every click and no PUT /api/auth/theme ever fired.
   The wood-paneling sibling always used the correct expression form,
   which is why the panel half-worked. Fixed to the interpolated form;
   TestThemePickerHandlersAreInterpolated pins that real theme names
   reach the HTML and the raw identifier never does.

2. Filter-builder op dropdown "does nothing": the field ingest
   hardcoded `ops: []` into every field's meta while only mirroring the
   ops into the global label registry — opsFor() returned [] for EVERY
   field, so the op menu rendered zero items: an invisible menu, no
   console error (user tried author/publisher/title/subtitle, all
   equally dead). FieldMeta.ops is now the wire's op objects, opsFor()
   is a standalone exported helper, and opsForField unit tests pin the
   round-trip. Verified live: the field menu opens/closes while the op
   menu stayed shut, both with identical wiring — the difference was
   the data, not the wiring.

3. AND/OR connective chip dead: the chip carried an `if` STATEMENT in
   the Alpine attribute (`@click="if (row.chipClickable) ..."`) which
   the CSP build's evaluator rejects as a statement — the whole
   expression silently never ran. Moved the clickability check into a
   toggleConnective(row) component method; the attribute is now a plain
   method call.

4. Pencil vs card navigation race: navigateToCollection guarded with
   `event.target instanceof HTMLElement`, which is FALSE for the
   pencil glyph's SVGElement — a click landing on the glyph sailed past
   the guard and navigated while the htmx edit-modal request still
   fired (the reported "modal flashes, then the builder page"). The
   guard now uses target.closest("button") (works on SVGElement) and
   takes $event explicitly instead of the deprecated window.event.
   .icon-btn is already a 36px square, so no hit-area change needed.

5. Add Items modal under the sidebar + taller than the window: the
   picker overlay sat at z-50 UNDER the app-sidebar's z-60 (its left
   edge rendered beneath the nav), and the card had no height bound —
   header + tabs + filters + grid + footer overflow short windows with
   the footer unreachable (fixed overlay, no page scroll). The picker
   and create-modal overlays move to z-[65], both confirm dialogs to
   z-[70], and the picker card is now a flex column capped at
   max-h-[85vh] whose grids flex-fill (they grow on tall windows,
   shrink on short ones). The ladder is documented at .app-sidebar in
   input.css: sidebar 60 / overlays 65 / confirm 70 / toasts 9999.

Found by clicking every control the way a user does (panel clicks +
computed-style reads + screenshots) after the previous sweep trusted
DOM-text snapshots, which show hidden menus' text and cannot see
occlusion, stacking, or geometry at all.

web/static/input.css

@@ -490,6 +490,17 @@
     --topbar-h: 4rem;
   }
 
+  /* ── Z-INDEX LADDER (app chrome) — keep new layers on this ladder:
+       60   .app-sidebar (and 55 its mobile backdrop)
+       65   app overlays: modals & pickers (z-[65]) — ALWAYS above the
+            sidebar; z-50 here painted the Add Items picker's left edge
+            under the sidebar (user report 2026-10-31)
+       70   sitewide #confirm-modal and any confirm inside an overlay
+            (z-[70]) — a confirm must never render under the dialog
+            that triggered it
+       9999 toasts (toast.ts)
+       Reader-scoped layers (backdrop 45, drawer 50, popover 60,
+       help 70/71) live on their own page without the sidebar. */
   .app-sidebar {
     position: fixed;
     top: 0;