feat: redesign thinking and web search UI per Figma specs (#650)

* feat: redesign thinking and web search UI per Figma specs

- Redesign "Thinking" UI: warning-colored bulb icon, placeholder-colored
  1px left border centered under icon, underline title
- Redesign "Web Search" UI: pill with gray/brand toggle on expand,
  success-colored globe and check icons, horizontal scrollable result cards
- Merge consecutive web_search tool calls into single grouped pill with
  combined result count
- Add "Search unsuccessful" state for empty search results
- Add ParseLinkUI with same pill style but text content on expand
- Fix Bing search HTML parser: handle new a.tilk structure, null-safe
  DOM access for both bing.ts and bing-news.ts
- Fix bubble layout table overflow: horizontal scroll within msg-content

Made-with: Cursor

* fix: resolve thinking flicker and add search queries to web search group

- Prevent thinking/done state flicker during streaming by locking transition
- Show search queries in expanded web search group UI
- Make thinking state expandable to view live reasoning content
- Add copy button to expanded thinking state

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: deduplicate reasoning collapse and improve web search expandability

- Extract shared reasoning collapse block to reduce duplication between
  thinking and done states
- Allow expanding web search group when queries exist even without results

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: validate snippet field in extractSearchResults type predicate

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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Co-authored-by: Suri Huang <surihuang@Suris-MacBook-Pro.local>
Co-authored-by: themez <themezeng@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>