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>

Migrate storage to PostgreSQL with SQLite fallback; misc fixes ...

- Add PgSessionStore (asyncpg pool) and PgMemoryStore replacing aiosqlite
- Keep SqliteSessionStore + SqliteMemoryStore for zero-dependency quick start
- Selection logic in deps.py: DATABASE_URL set → PG, else → SQLite
- Add asyncpg>=0.29 to dependencies; add DATABASE_URL / DB_PATH to config
- Add RESPONSE HYGIENE rule to persona: never echo tool output or plan state
- Add developer profile user tools: weather, internal_monitor
- Update README: developer profile, DB section, current tool/profile state

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

Major feature batch: visibility, planning, file uploads, streaming ...

- stream_complete(): streaming with tools for all LLM turns — thinking
  now streams as ThinkingDelta/ThinkingEnd in real-time during tool-
  selection turns, not just on the final response
- todo built-in tool: session-scoped plan manager (set/view/update/clear);
  persona + all profiles updated with mandatory planning instructions
- TurnThinking event: sub-agent thinking forwarded to parent sink as a
  collapsible block in the spawn_agent card
- File uploads: non-image files uploaded via XHR, shown as badges in
  message bubble; SVG treated as regular file (not base64 image)
- session_files: POST /sessions/{id}/files, TTL cleanup, forbidden exts
- WebSocket reconnect: _AgentRun broadcast pattern, re-attach mid-stream
- UI: favicon, sidebar logo, turn-thinking cards, subagent thinking blocks,
  token counter, draft persistence, file progress bar
- Removed AgentNote (content is always None alongside tool_calls)
- Ollama stream_complete: tool_calls captured from non-final chunk (done=False)

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

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

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