chore: chat and related fixes

[ussaama]

implementation instead of three drifting copies

• Fix classic Specific Details to show "Context added" instantly on send, replacing a fragile history-refetch race with a local stand-in that's swapped for the real message once history reconciles
• Fix scroll-to-bottom detection for chats that render their thread after an initial loading/mode-picker screen; the anchor-wait path now uses a scoped MutationObserver (via a new data-app-scroll-root marker) instead of a busy per-frame poll
• Give agentic template pills their mode-accent border and fix long labels overflowing instead of truncating
• Add a count-only mode to ConversationFocusChips and use it on the New Chat picker screen, removing a duplicated hand-rolled chips block
• Add a disabled prop to ConversationFocusChips, separate from isClearing, so blocking the control for unrelated reasons doesn't misuse the clear-action's own loading state
• Revert the agentic error-message masking added earlier in this branch (agentic_worker.py) to redo it together with a related prompt fix, rather than ship a half-finished whitelist
• Add test coverage for the previously untested ConversationFocusChips precedence rules and the useStickToBottom hook's container resolution, scroll-target selection, and resize/mutation-driven remeasurement