Collection pane: searchable bookmark feed (+ container-pane support) #73

Follow-up to #69/#71. Adds a collection view for /public/bookmark/ and the small browser change needed to support it.

Browser change (general, in data-browser-panes.js)

Panes are now offered containers as well as single resources:

• render may be async and may return null/'' to decline (the browser then falls through to the folder table / JSON — no regression for ordinary folders).
• h gains isContainer, path, children (parsed members), and fetchResource(url) (async → a child's primary node), so a pane can render a collection.

A resource pane (keyed on @type) naturally won't match a container, and a container pane that doesn't recognise a folder returns null — so existing folders still render the file table.

Collection pane (examples/panes/bookmark-collection.js)

canHandles the conventional /public/bookmark/ container and renders its bookmark:Bookmark members as a searchable feed:

• compact cards (favicon, title, host, 2-line summary snippet, tags), newest first
• a search box filtering live over title + summary + tags + host (self-contained inline oninput handler — a <script> wouldn't run via innerHTML)
• card body → the bookmark's .jsonld detail page (the full single-card summary); a corner ↗ opens the original external link
• returns null if the folder holds no bookmarks (falls back to the folder table)

No version bump

Deliberately not bumping. The data-browser-panes.js change lands on gh-pages but won't hit the cdn until a future publish; running pods can pick it up via a local --mashlib-module override until then. Reference pane, schema.org vocab reused.