fix(react-ui/chat): stop wiping selection on every /api/operations poll (#9904) (#9917)

useOperations() was calling setOperations() with a fresh array on every
1s poll, even when the payload was identical. In React 19 the DOM diff
no longer short-circuits dangerouslySetInnerHTML on equal __html, so the
forced Chat re-render re-assigned innerHTML on every assistant message
once per second — wiping any text the user had selected.

Skip the state update when the serialised operations payload is
unchanged, and switch loading/error to functional setters so they also
short-circuit at the source.

Also fixes the chat copy button on plain HTTP: navigator.clipboard is
undefined in non-secure contexts (a common LXC+Docker deployment), but
the previous code called it unconditionally and showed a success toast
regardless. Routed Chat, AgentChat and CanvasPanel through a new
copyToClipboard() helper that uses navigator.clipboard when available
and falls back to a hidden-textarea + execCommand('copy') trick that
browsers still honour outside secure contexts. The fallback preserves
the user's existing selection.

Regression coverage in e2e/chat-polling-selection.spec.js: a
MutationObserver counts mutations on the assistant content node across
3s of polling (must be 0); the copy test stubs out navigator.clipboard
and asserts that execCommand('copy') is invoked.


Assisted-by: claude-opus-4-7-1m

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>