Highlighter: Mark every line of a multi-line offense output

[marcoroth]

This pull request updates the Highlighter's diagnostic renderers so an offense that spans multiple lines is marked on every line it covers, instead of drawing a single marker on the start line using the end line's column.

Both renderers computed the marker as end.column - start.column anchored at start.column, and never looked at location.end.line at all. For an offense spanning (26:4) to (28:13) that produced a marker on line 26 running from column 4 to column 13, which is neither where the offense starts nor where it ends:

     24 │
     25 │   <div id="gems" class="grid min-w-full gap-4 sm:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4">
  →  26 │     <% @gems.each do |topic_gem| %>
        │     ~~~~~~~~~
     27 │       <%= render partial: "gem_card", locals: {topic_gem: topic_gem} %>
     28 │     <% end %>

Now every spanned line gets an arrow and a marker: the first line from start.column, the last line up to end.column, and the lines in between across their non-whitespace content. The trailing context also runs off the end line rather than the start line, so the lines after the offense are actually visible:

     24 │
     25 │   <div id="gems" class="grid min-w-full gap-4 sm:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4">
  →  26 │     <% @gems.each do |topic_gem| %>
        │     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  →  27 │       <%= render partial: "gem_card", locals: {topic_gem: topic_gem} %>
        │       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  →  28 │     <% end %>
        │     ~~~~~~~~~
     29 │   </div>
     30 │

The marker geometry moves into a new computeDiagnosticMarkers() helper in diagnostic-markers.ts, shared by both renderers so the split view (herb-lint detailed output) and the whole-file inline view stay consistent. It returns one marker per line and skips lines with nothing to mark, so a blank line inside a span stays unmarked rather than collecting a stray marker.

In the inline renderer the diagnostic message now renders under the last spanned line instead of the first, so it no longer sits wedged between the source lines of its own offense:

  →   2 │   <% @gems.each do |topic_gem| %>
        │   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  →   3 │     <%= render partial: "gem_card" %>
        │     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  →   4 │   <% end %>
        │   ~~~~~~~~~
        │   [warning] Multi-line offense (multi-line-rule)

Resolves #1982

[github-actions]

🌿 Interactive Playground and Documentation Preview

A preview deployment has been built for this pull request. Try out the changes live in the interactive playground:

• Playground Preview
• Documentation Preview
• Website Preview

---

_{🌱 Grown from commit 6393212}

---

✅ Preview deployment has been cleaned up.

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@1999

npx https://pkg.pr.new/@herb-tools/language-server@1999

npx https://pkg.pr.new/@herb-tools/linter@1999

commit: 6393212