## Summary
Rebased on behalf of @aronprins from fork branch `codex/dark-user-bubbles`. Two asset-only commits (PR screenshot add/remove) were dropped; the two code commits are applied cleanly on top of current master (v0.50.110).
### What changed
**Dark-mode user bubbles** (`static/style.css`):
- `:root.dark` now overrides `--user-bubble-bg`/`--user-bubble-border` to `var(--accent-bg-strong)` (a 15% opacity tint) — keeps the bubble visually subdued in dark skins instead of a glaring bright accent fill
- Removes 6 per-skin `--user-bubble-text` hacks (ares, mono, slate, poseidon, sisyphus, charizard); text falls back to `var(--text)` which is already correct in dark mode
- Adds `--user-bubble-placeholder` token; edit-area box-shadow now uses `--focus-ring` instead of hardcoded `rgba(255,255,255,.15)`
**Thinking card collapsibility** (`static/ui.js` + `static/style.css`):
- `_thinkingMarkup()` now includes `onclick` toggle and chevron affordance, matching the compression reference card pattern
- `.thinking-card-header` gets `display:flex; gap:8px` for proper icon/label/chevron alignment
**Tests**: 2 new in `test_bugbatch_apr2026.py` (dark bubble token contract + no-per-skin-hack assertion), 2 updated in `test_ui_card_animation.py` (flex header layout + onclick pattern).
1520 passed. QA 20/20. Browser verified: dark mode bubble uses subtle tint, thinking card toggles correctly.
(credit: @aronprins)
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