Clean up SQLite references in docs and prompts after removal ...

- docs/index.md: PostgreSQL via asyncpg
- docs/memory.md: drop aiosqlite fallback mention
- docs/sessions.md: replace SqliteSessionStore with PgSessionStore docs
- webclient/docs/architecture.md: PostgreSQL only
- navi/profiles/tool_developer/system_prompt.txt: remove aiosqlite from available imports
- .gitignore: add .codex and *.db
- No remaining sqlite/aiosqlite/db_path references in codebase

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Remove SQLite legacy support ...

SQLite is no longer supported; PostgreSQL is now required.

- Delete navi/core/sqlite_session_store.py
- Delete navi/memory/sqlite_store.py
- Remove SqliteSessionStore from navi/core/__init__.py exports
- deps.py: drop SQLite fallback, raise RuntimeError if DATABASE_URL missing
- config.py: remove db_path setting
- pyproject.toml & requirements.txt: drop aiosqlite dependency
- .gitignore: remove navi.db entry
- tech_debt_review_2026-04-29.md: mark #8 as REMOVED

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Add Ollama multi-server fallback with in-memory blacklisting ...

- New FallbackOllamaBackend (navi/llm/fallback.py): tries servers and
  models in priority order; on LLMConnectionError blacklists the server
  for the process lifetime, on LLMModelNotFoundError blacklists the
  (server, model) pair — eliminates latency from repeated failed probes
- OllamaBackend now raises typed LLMConnectionError / LLMModelNotFoundError
  instead of bare LLMBackendError; accepts list[str] | str | None for model
- AgentProfile.model changed from str to list[str] (str auto-normalised);
  all profiles updated to ["gemma4:31b-cloud", "gemma4:26b-a4b-it-q4_K_M"]
- New config field OLLAMA_BACKENDS_FILE: path to [{host, api_key?}] JSON;
  when set, registry creates FallbackOllamaBackend instead of OllamaBackend
- ollama_backends.json template added (gitignored — contains API key)
- current_model ContextVar type widened to list[str] | str | None

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

Migrate to Vue webclient; rename old client to old_webclient ...

- client/ → old_webclient/ (vanilla JS client preserved as reference)
- webclient/ — new Vue 3 + Pinia webclient (source + dist build)
- vite.config.js: outDir changed to webclient/dist/
- main.py: serve /assets and /images from webclient/dist/,
  index.html from webclient/dist/index.html
- .gitignore: exclude webclient/node_modules/, include webclient/dist/

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

Add workspace dir + clean up junk from project root ...

- workspace/ — persistent dir for Navi's long-term files (scripts, notes,
  data); excluded from git, Navi instructed to use it instead of project root
- .gitignore: session_files/ and workspace/* added
- persona.txt: WORKSPACE section pointing Navi to workspace/
- Deleted scanner.py, network_scan_results.txt, targets.txt (Navi artifacts)

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

Update .gitignore: ignore tmp files and tool data files ...

Add .tmp, task_manager.json, tools/*_data.json (runtime data written
by user tools like user_notes). Remove brain_kb.py (broken syntax).

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

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

Unrestricted terminal mode and SSH tool ...

- Terminal: TERMINAL_ALLOWED_COMMANDS=* (default) runs via shell,
  supports pipes, redirects, subshells; allowlist mode still available
- FS_ALLOWED_PATHS expanded to cover /home /etc /var /opt
- New ssh_exec tool: execute commands on remote hosts via asyncssh,
  supports named connections (ssh_hosts.json) and inline user@host
- ssh_hosts.json gitignored, ssh_hosts.json.example added as reference
- ssh_exec added to server_admin and smart_home profiles

Initial implementation of the agent system core ...

- FastAPI server with REST API and WebSocket streaming
- Modular LLM backend abstraction (Ollama implemented, OpenAI stub)
- Tool system: web_search (ddgs), filesystem, http_request, code_exec, terminal
- Agent profiles: smart_home, server_admin, secretary
- Tool-calling loop with concurrent tool execution
- In-memory session store with SessionStore ABC for future persistence
- Registry pattern for tools, profiles, and backends
- Orchestrator stub as foundation for multi-agent scenarios