No reachable path to comments 11..N

Problem/Motivation

With progressive loading and the shipped defaults, only the first N sibling comments render (24 of 216 on a test node), yet the header reports the full count. The only affordance is per-branch expansion; there is no across-siblings control to reach the remaining roots. The show-all URL and per-comment remaining count are computed but never rendered, and the show-all query key embeds a settings hash a reader cannot construct.

Steps to reproduce

• Open a node with 200+ comments under ACT.
• Note the header reports the full count while only ~24 comment rows are present.
• Search the rendered page: no control reveals roots 11..N.

Proposed resolution

• Render show_all_url as a real link in comment-list.twig.
• Add a per-sibling-group "N more replies" affordance backed by the computed remaining count.
• Make the show-all parameter constructible by a reader, or replace the embedded settings-hash key with a stable key.

Remaining tasks

• Verify the full thread is reachable on a 200+ comment node.

User interface changes

Adds the missing "show all / N more" controls and the reachable full-thread path.

API changes

The show-all query parameter name becomes stable and constructible.

Data model changes

None anticipated.

AI-Generated: Yes (Used Opus 5 and DeepSeek Flash to review and discover these issues)