Feature request: Add "Quote selection to reply" in the chat UI.

• Select text within a single message and show a small floating icon-only quote affordance near the selection
• Display a compact quote preview above the composer with a dismiss control
• On send, prepend a standardized context quote block:

[context]

line 1
line 2
[/context]

• Optional keyboard shortcut: Cmd/Ctrl+Shift+Q

Benefit: Enables clearer, scoped replies without changing existing chat virtualization behavior.