Client UX: profile-filtered sessions, draft persistence, stream safety ...

- Profile selector now filters session list: only sessions of the selected
  profile are shown; switching profile opens the most recent session for
  that profile (or empty state if none exist)
- openSession() syncs profileSelect to the opened session's profile so
  the list always reflects what's on screen
- Session items no longer show redundant profile name (list is filtered)
- Bug fix: switching sessions while streaming now calls abandonStream()
  before ws.disconnect() — resets state without touching DOM, preventing
  WS onClose from calling finishStream() on the wrong session
- Textarea no longer disabled during streaming — only the Send button is
  locked; user can type the next message while model is still responding
- Draft auto-saved to localStorage per session on every keystroke, restored
  on session switch, cleared on send — survives page refresh

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Add context token counter: 64k default, live UI display ...

- config: ollama_num_ctx default 8192 → 65536
- LLMChunk: add prompt_tokens / completion_tokens fields
- OllamaBackend.stream: populate token counts from final chunk
  (prompt_eval_count + eval_count when chunk.done)
- StreamEnd: add context_tokens and max_context_tokens
- Agent.run_stream: capture token counts, pass to StreamEnd
- websocket: include context_tokens / max_context_tokens in stream_end
- index.html: split chat-header into title span + token-counter span
- sidebar.js: updateChatHeader targets #chat-header-title, not innerHTML
- app.js: updateTokenCounter() shows "X/Y (Z%) tokens", colors:
  gray <50%, amber 50–79%, red ≥80%
- style.css: .token-counter, .warn, .danger styles

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Add multimodal image support and client UX improvements ...

Server:
- Add ImageViewTool (load image from file/URL, returns base64)
- Add images field to Message model with created_at timestamp
- Agent run/run_stream accept images param; inject image messages after image_view tool calls
- WebSocket handler accepts images array from client, strips data URI prefix
- All profiles include image_view tool
- Fix tool call serialization (model_dump mode=json for datetime)
- Add no-store cache headers for static files

Client:
- Image attachment: file picker button + clipboard paste + preview strip with remove
- Images rendered in chat bubbles; loaded from history
- Tool cards rebuilt as div+CSS toggle (fixes details/overflow-hidden collapse bug)
- Tool cards appear before response bubble (lazy bubble creation on first stream_delta)
- Typing indicator persists through tool calls, removed only when text starts streaming
- Tool cards restored from history on page reload
- Message timestamps stored via created_at field, shown correctly in history
- Session ID reflected in URL hash for bookmarking; restored on page load
- Remove localStorage session tracking (server last_active used instead)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Markdown rendering, syntax highlighting, tool card accordion ...

- marked.js (v12) renders assistant messages as markdown
- highlight.js (v11) highlights code blocks with atom-one-dark theme
- During streaming: raw text; on stream_end: rendered to markdown
- Tool cards redesigned as <details> accordions:
  - Shows tool name, icon, success/fail indicator
  - Click to expand: arguments grid + scrollable result pre
  - Slide-in animation on open

Persistent sessions and client module refactor ...

Server:
- SqliteSessionStore replaces InMemorySessionStore as default backend
- Sessions survive server restarts (stored in navi.db)
- DB_PATH configurable via .env

Client:
- Split monolithic app.js into ES modules:
  js/api.js    — REST calls
  js/ws.js     — WebSocket wrapper (WsClient class)
  js/chat.js   — message area DOM helpers
  js/sidebar.js — session list and header helpers
  js/app.js    — state, wiring, boot
- Active session persisted in localStorage — restored on page reload

Add web chat client ...

- Single-page chat UI served as static files from FastAPI
- Sidebar with profile selector, new chat button, session list
- WebSocket streaming: shows tool calls and text deltas in real time
- Typing indicator, streaming cursor, auto-resize textarea
- Session history loads on switch