a11y: replace table-as-layout markup with semantic elements

[m5x5]

Summary

• The outline and data-content panes built predicate/value lists, rdf:List members, and per-subject blocks as <table>/<tr>/<td>. Screen readers announced them as data tables with rows and columns, which they aren't.
• appendPropertyTRs now emits <dl class="property-list"> with one <dt> per predicate and one <dd> per value, replacing <tr>s with rowspan tricks for repeated subjects.
• outlineObjectTD / outlinePredicateTD take an optional elementName argument so callers in non-table contexts (folder-pane list items, property-list <dd>s) get a <div> instead of a stray <td>.
• The object-cell expand affordance becomes a native <details>/<summary> with a lazy toggle listener — drops the custom expand-icon image and the click wiring around it.
• rdf:List rendering (Collection branch) switches from <table class="collectionAsTables"> to <ol class="rdf-collection"> with the browser's native marker numbering.
• dataContentPane per-subject blocks become <section>s with a <dl class="property-list">; nested bnodes get a .nestedBnode class instead of being rendered as nested striped tables.
• Fix Graph branch crash: paneRegistry.byName('dataContentPane') is not a registered name — use 'dataContents' and fall back to a text node if lookup still fails.
• Surface swallowed errors: catch sites in manager.js and userInput.js now console.error(e) in addition to rendering the exception pane, so DevTools shows the stack trace.

Addresses SolidOS/profile-pane#310.

Coordinated PRs

• a11y: promote .app-view to the page-level <main> landmark mashlib#394 — Promote .app-view to the page-level <main> landmark
• a11y: demote tab-widget body from <main> to <div> solid-ui#747 — Demote tab-widget body from <main> to <div>
• a11y: drop inner <main> from ProfileView and EditProfileView profile-pane#312 — Drop inner <main> from ProfileView and EditProfileView
• SolidOS/folder-pane (a11y/list-of-resources) — Render LDP container contents as <ul>, not a 2-column <table>