pax a86941decf info_panel: suppress flat-tag flash when category fetch is pending
When a category fetch is about to fire (Rule34/Safebooru.org/
Moebooru on first click), the info panel was rendering the full
flat tag list, then ~200ms later re-rendering with categorized
tags. The re-layout from flat→categorized looked like a visual
hitch.

Fix: new _categories_pending flag on InfoPanel. When True, the
flat-tag fallback branch is skipped — the tags area stays empty
until categories arrive and render in one clean pass.

  _ensure_post_categories_async sets _categories_pending = True
    before scheduling the fetch (or False if no fetcher = Danbooru)
  _on_categories_updated clears _categories_pending = False

Visual result:
  Danbooru/e621:        instant (inline, no flag)
  Gelbooru with auth:   instant (background prefetch beat the click)
  Rule34/SB.org/Moebooru: empty ~200ms → categories appear cleanly
                          (no flat→categorized re-layout)
2026-04-09 20:05:38 -05:00
..