Keyboard, screen reader and contrast fixes from the interface review (#298 #299 #300 #301 #302 #303 #304 #305 #306 #307 #308 #309)

Found reviewing the main window, its dialogs and the Directory in all 25 palettes (13 themes,
light and dark), in Playwright against the test daemon.

- #298: an item's title is a button, so Tab and a screen reader can open it; the feed list's
  rows, places, Signals and the Directory's shows are links to a screen reader (asLink), named
  by what they show, the open one aria-current. Not role=button, which would flatten a folder's
  triangle inside it.
- #299: .ep:focus-within shows the row's actions; Tab reached Play and Delete at opacity 0.
- #300: the read toggle is named Mark read / Mark unread, the dot hidden from screen readers.
- #301: the seek slider is named Position, its value read as "12:30 of 45:00".
- #302: ::placeholder in --faint; the browser's grey was 2.7-4.4:1 in 20 palettes. The search
  and filter boxes have names that do not depend on their placeholder.
- #303: #toasts is role=status; an error toast stays until dismissed, at most four at once.
- #304: api() says what to do when iPX cannot be reached or answers 500 (whose text is the
  daemon's internals, already in its log); play() failures are put in words and reported, an
  AbortError ignored; a failed download names its item.
- #305, #308: --field, the theme's --fg mixed into --bg in OKLab (--fieldmix, 60% and up to 80%
  for Catppuccin light), edges text boxes, selects, chips, the OPML box and switch tracks,
  phones included, and rings a light theme's switch knob. tests/contrast.js holds it to 3:1 on
  bg, panel, panel2 and raise in every palette. --line stays for rules. Fields lose outline:0,
  so they take the same focus ring as everything else.
- #306: openModal makes the card role=dialog aria-modal, labelled by its heading, focuses it,
  and makes the rest of the body inert until closeModal, which gives focus back to what opened
  it. Not <dialog>: its top layer would cover the toasts and their Dismiss.
- #307: the labels in Add a feed, Settings, Download latest and OPML point at their boxes.
- #309: Settings shows iPX's and the page's versions at its foot.

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

web/src/feeds.ts

@@ -105,6 +105,7 @@ function renderFeeds(){
     el.tabIndex=0; el.dataset.id=id;
     el.innerHTML=`<span class="ico">${v.icon}</span><b>${v.title}</b>`+(id===':all'
       ?`<span class="badge${unreadAll?'':' zero'}" title="${unreadAll} unread">${unreadAll>999?'999+':unreadAll}</span>`:'');
+    asLink(el,S.feed===id);
     el.onclick=()=>{ selectFeed(id); nav(false); };
     el.onpointerenter=el.ontouchstart=()=>prefetch(id);
     places.appendChild(el);
@@ -168,6 +169,7 @@ function renderFeeds(){
       `</small></div>`+
       (f.orphaned?'<span class="tag" title="No longer listed, kept because it has downloads">Gone</span>':'')+
       `<span class="badge${unread?'':' zero'}" title="${unread} unread">${unread>999?'999+':unread}</span>`;
+    asLink(el,S.feed===f.id);
     el.onclick=()=>{ selectFeed(f.id); nav(false); };
     // Fetched as the pointer or a finger reaches it, so the click finds it here (#247).
     el.onpointerenter=el.ontouchstart=()=>prefetch(f.id);