feat: TUI overhaul — animation, widgets, layout, modals, streaming, theme system

[ruttydm]

Summary

Massive TUI overhaul implementing the full plan from docs/proposals/tui-overhaul-master-plan.md. 188 files changed, ~72K lines added.

Key Systems

• Animation system — TuiAnimationManager with breathing effects, spinners, phase-based animations, signal-based timing
• Widget library — TreeWidget (lazy-load, expand/collapse), TableWidget, TabsWidget, StatusBoardWidget, EditorWidget, MarkdownWidget with custom stylesheet
• Modal system — TuiModalManager with overlay dialogs, settings, session picker, plan approval, user questions
• Toast notifications — non-blocking inline feedback
• Theme system — Theme class with shared color palette, tool icons, context bar; KosmokratorTerminalTheme for syntax highlighting
• Layout engine — Composer-based layout with header/context bar/conversation/input zones
• Streaming renderer — Real-time LLM response streaming integrated with Revolt event loop
• Subagent display — SubagentDisplayManager with live tree widget, progress bars, swarm dashboard

Commits

• ba22775 — docs: add TUI overhaul master plan and sub-plans
• ced594e — feat: TUI overhaul — animation, signal, widget, theme, layout, modal, toast, streaming systems

Test Plan

• All widget unit tests pass (TreeWidgetTest, TableWidgetTest, TabsWidgetTest, TabItemTest)
• php vendor/bin/phpunit green
• php vendor/bin/pint clean
• Manual smoke test with bin/kosmokrator in TUI mode
• Verify ANSI fallback still works with --renderer=ansi