🎨 Palette: Enhance search UX and accessibility polish

[anaxifty]

🎨 Palette UX & Accessibility Polish

This PR implements several micro-UX improvements focused on accessibility, search intuitiveness, and interaction feedback.

💡 What

1. Accessibility (A11Y): Added aria-label attributes to all primary icon-only buttons (#sidebar-collapse-btn, #hamburger-btn, #attach-btn, #voice-input-btn, #chatSendBtn, #chatStopBtn) and marked decorative SVGs as aria-hidden="true".
2. Search Feedback: Introduced "No results found" messages for both the sidebar conversation search and the model selector search. These messages use role="status" and aria-live="polite" to ensure they are announced by screen readers.
3. Search State Management: Modified renderSidebar to preserve search filters when pinning/unpinning or deleting chats. The search input is now explicitly cleared when a user clicks "New Chat" to provide a fresh state.
4. Interaction Feedback: Enhanced the code block "Copy" button to temporarily change its text to "Copied!", providing immediate confirmation at the point of click.
5. Journaling: Initialized .Jules/palette.md to track UX and accessibility patterns.

🎯 Why

Icon-only buttons are inaccessible to screen reader users without labels. Empty search results without feedback can lead users to believe the app is broken or frozen. Preserving search state during common interactions reduces friction, while clearing it for "New Chat" matches user expectations for a clean slate.

♿ Accessibility

• Semantic labels for all icon buttons.
• ARIA live regions for dynamic search feedback.
• Improved keyboard interaction flows by managing search state correctly.

---

PR created automatically by Jules for task 10908678206566346302 started by @anaxifty

[cloudflare-workers-and-pages]

Deploying neuraldock with    Cloudflare Pages

Latest commit:	ce9af1b
Status:	✅  Deploy successful!
Preview URL:	https://7efc339f.neural-dock.pages.dev
Branch Preview URL:	https://palette-ux-a11y-polish-10908.neural-dock.pages.dev

View logs

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.