Quality overhaul: code tooling, CI/CD, architecture diagrams, UI rede… (#1)

* Quality overhaul: code tooling, CI/CD, architecture diagrams, UI redesign, and legacy cleanup

- Add ruff (lint+format) and mypy (strict) with zero errors across 37 source files
- Add GitHub Actions CI (lint, typecheck, test matrix 3.11/3.12/3.13) and PyPI publish workflow
- Create 12 PlantUML architecture diagrams with PNG renders covering all subsystems
- Refresh README and docs with badges, diagram links, and current descriptions
- Refactor test_server_live.py with mock streaming helpers for deterministic CI testing
- Update dependencies to current versions (openai>=2.24, httpx>=0.28, redis>=7.2)

Console dashboard:
- Move state indicators from top cards to fixed bottom status bar with cluster metrics
- Replace flat 50-node list with hostname-prefix grouped nodes (expand/collapse, up to 1000)
- Apply "Instrument Panel" visual redesign: IBM Plex Mono + Outfit fonts, warm amber accent,
  LED glow state indicators, deep charcoal surfaces, WCAG AA contrast compliance
- Add render cache, stale indicator, active filter highlight, loading states

Server web UI:
- Apply matching Instrument Panel aesthetic for visual consistency with console
- Fix branding (pcode → turnstone), extract inline styles to CSS classes
- Rename pcode localStorage keys and history state to turnstone

Legacy cleanup:
- Remove persona-model-specific --persona flag and /persona slash command
- Remove model_identity from chat_template_kwargs (vLLM-specific mechanism)
- Refactor plan agent to use standard developer message instead of model_identity
- Remove dead code (unused date/has_tools variables, noqa suppressions)

* Fix CI typecheck: add mypy overrides for optional sympy/numpy imports

The math sandbox optionally imports sympy and numpy at runtime (try/except
ImportError). In CI these packages are not installed, so mypy raises
import-not-found rather than import-untyped. Add mypy overrides to
ignore missing imports for these optional dependencies.

* Fix Copilot review findings: ARIA role, status bar cache, and pulse opacity

- Change #node-table from role="tree" to role="list" and group elements
  from role="treeitem" to role="listitem" (proper ARIA semantics)
- Include currentView and currentFilter.state in renderStatusBar cache key
  so active pill highlight updates when switching views
- Align pulse animation to 0.35 opacity (already applied in CSS)

docs/diagrams/png/03-core-engine-classes.png

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