#296 r3: shrink URL column, render URL values as plain text

Owner override postdating PR #300 QA pass:
- .col-url 340 -> 230px; reclaim slack from history-only columns (Views 96->90,
  Created 190->150, ID 190->120) so the table fits the .float pane with no
  horizontal scroll at 1400x900 and the ID column is fully visible.
- URL anchors drop the shared .slug pill (background/padding/radius/mono font)
  and render plain, styled via td.dim exactly like the none case; links stay
  anchors with accent hover. Ellipsis kept for genuinely long slugs.

Verified by CDP probe on a local build at 1400x900 and 375x812 on /public and
/mine (/saved): column order, table fits pane (scrollWidth == clientWidth),
20-char slug fully visible, min Created-to-URL content gap 77px, sort arrows
intact 6px right of labels, no CSP/console violations. go build/test pass.

internal/web/static/history.js

@@ -11,7 +11,7 @@ const t = PaletteTable.init({
     `</td>` +
     `<td><span class="badge">${t.esc(it.type || it.language || 'text')}</span></td>` +
     `<td class="dim">${t.fmtSize(it.size)}</td><td class="dim">${it.view_count}</td><td class="dim" data-ts="${it.created_at}">${t.ago(it.created_at)}</td>` +
-    (it.custom_slug ? `<td><a class="slug url-link" href="/${t.esc(it.custom_slug)}">/${t.esc(it.custom_slug)}</a></td>` : `<td class="dim">none</td>`) +
+    (it.custom_slug ? `<td class="dim"><a class="url-link" href="/${t.esc(it.custom_slug)}">/${t.esc(it.custom_slug)}</a></td>` : `<td class="dim">none</td>`) +
     `<td class="dim"><a class="id-link" href="/${t.esc(it.id)}">${t.esc(it.id)}</a></td></tr>`,
   emptyFiltered: 'No pastes match your search.',
   emptyAll: 'No pastes yet. Create the first one.',