feat: lib-agent-dock-ui — global assistant dock

@crema/agent-dock-ui — a floating Sparkles FAB that opens a right-side
slide-over chat with an agents-platform agent. Extracted from
skyai-finance (the canonical dock) and made app-agnostic.

The shell, threading, compose box, and rich-block rendering (via
@crema/agent-ui's MessageBody) live here; the app injects identity
(resolveAgents), context (getPageContext → structured PageContext),
and transport (auth closed over inside it — the dock never sees a
token). Self-contained: raw slide-over + buttons styled with theme
tokens, no app-local shadcn dependency. Page context travels as a
structured field, never concatenated into the message.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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