feat: add recently added missing code from default-ui

[mmattel]

This PR adds recently added missing code from the default-ui.

Tested locally, works

[DeepDiver1975]

🤖 Automated review by Claude Code review agent.

Overview

This PR adds a single {{#if ./latest.navigation}} guard around each component <li> in src/partials/nav-explore.hbs, porting a change that already exists in the upstream Antora default-ui. The effect: components whose latest version exposes no navigation are no longer rendered in the explore panel's component list. The change is +2/-0 lines, one file.

Code quality / style

• The added lines follow the existing indentation and Handlebars conventions in this file (block helpers placed on their own lines, ./ context-relative references consistent with the surrounding ./url, ./versions, etc.).
• I diffed the modified partial against the current upstream antora-ui-default nav-explore.hbs. The block structure is an exact match: {{#if ./latest.navigation}} opens immediately after {{#each site.components}} and closes right before {{/each}}, wrapping the full <li class="component">…</li>. Bracket/nesting balance is correct.

Specific suggestions

• None required. This is a faithful, minimal upstream sync.
• Optional (non-blocking): a one-line comment or a reference to the upstream commit in the PR description would help future maintainers understand why the guard exists, but this is not necessary.

Potential issues / risks

• Behavioral change to be aware of: any component whose latest version has no navigation (latest.navigation falsy) will now be hidden from the explore sidebar entirely — including its version sublist. This matches upstream intent and is almost certainly the goal, but it is a visible behavior change rather than a pure no-op. The author notes "tested locally, works," which covers the happy path.
• latest.navigation is evaluated on the component's latest version while the version loop below still iterates all ./versions. This is consistent with upstream and fine: a component with a navigation-bearing latest version still lists older versions normally; the guard only suppresses components whose latest has no nav.
• Scope is limited to this one partial. I confirmed site.components is iterated in exactly one place in src/, so there is no sibling template needing the same guard for consistency. No bundling/JS/build config is touched, so no regression risk there.

LGTM. Correct, minimal, and consistent with the upstream default-ui reference.