tools: a non-admin may reach their own session directory ...

A non-admin was confined to user_data/<user_id>/ alone, which made four
tools reject the directory the user's own uploads land in: share_file
refused the file it was asked to send back, filesystem could not read it,
and terminal/code_exec could not be pointed at it. In a prod session the
agent worked around the refusal by copying the uploaded file into its
sandbox with code_exec — the very bypass the injected security policy
forbids — and the copy collided with a same-named file, so the user got a
link to Project_1.mp3 instead of their own upload, plus an 8.6 MB duplicate.

navi/tools/_internal/areas.py now names the two roots a user owns, and the
four call sites share it. Relative paths still resolve into the sandbox,
and each tool keeps its own way of refusing: terminal returns
sandbox_violation, code_exec silently falls back to the sandbox root. The
share_file refusal lists both roots instead of "outside user sandbox", so
the agent retries in the right one instead of routing around it.

The session directory belongs to the same user: its id arrives from the
runtime context, never from tool arguments, and only the session's owner
can open it.

terminal: session-broadcast sink + lifecycle events (Etap 1) ...

Persistent terminals emitted their stream only into a per-tool-call sink, which
closed once the open action returned — so a background dev server's output
stopped reaching the client immediately after open. TerminalClosed was never
emitted at all (the handler existed, the emitter did not).

Replace the per-tool event_sink with a single callback the orchestrator wires to
the session's WebSocket(s):

- TerminalManager: set_event_callback(cb) + _emit(session_id, event). Reader
  tasks and open/close deliver TerminalOutputDelta / TerminalOpened /
  TerminalClosed through the callback, which lives for the terminal's (and
  session's) lifetime — not the tool call's.
- New TerminalOpened event (terminal_opened: name/description/pid/background).
  TerminalClosed now actually emitted from _close_one (explicit/idle/shutdown/
  session_ended). Background output keeps streaming after open returns.
- terminal.py: drop the per-tool event_sink from _tm.open (no longer needed).
- orchestrator._on_terminal_event → _notify_session (per-session WS fan-out,
  same path recall/mcp updates use). container wires the callback after building
  the orchestrator.
- Events imported lazily inside terminal_manager methods to avoid a circular
  import (navi.core.events → navi.core.__init__ → agent → registry → navi.tools).

Tests: open emits TerminalOpened; background output streams via the callback
after open returns (gap-3 fix); close emits TerminalClosed; no callback does not
break readers. Existing terminal tests unchanged. Full suite: 968 passed, 1 skipped.

Plan: docs/terminal_tool_plan.md (5 etaps, this is Etap 1).

Move terminal_manager to _internal subpackage ...

- terminal_manager is an internal helper, not a tool
- Update imports in terminal.py, container.py, test_terminal.py

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

Fix terminal review issues: security, lifecycle, reactivity ...

- TerminalManager.open now accepts exec_tokens to use create_subprocess_exec
  for restricted commands instead of always using shell
- Fix kill/terminate order: SIGTERM first, SIGKILL fallback
- Pop closed sessions from _sessions dict to prevent memory leak
- Add terminal_manager.shutdown() to AppContainer.shutdown()
- Wait for reader tasks in foreground open before returning output
- Add _MAX_TERMINALS_PER_SESSION limit (10)
- Wrap cleanup_idle tasks in _close_one_safe with error logging
- send_input catches BrokenPipeError/ConnectionResetError specifically
- Foreground terminals auto-close after gathering output
- Vue reactivity: replace terminals object immutably instead of mutating
- onTerminalClosed marks matching tool card as no longer pending
- Update tests for new behavior (foreground auto-close, max limit)

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

Add persistent multi-session terminal tool with background support ...

- New TerminalManager module: named subprocess sessions per Navi session,
  background readers, event-sink streaming, idle auto-cleanup
- Refactor terminal tool to multi-action: run, open, close, list,
  status, send_input
- Add TerminalOutputDelta and TerminalClosed events for streaming
- Wire TerminalManager into AppContainer, orchestrator, and registry
- Persist session_metadata in Session model and pg_session_store
- Close all session terminals on session delete
- Webclient: handle terminal_output/terminal_closed WS events,
  display live terminal output in tool cards
- Update unit tests for new terminal actions

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

Add 62 tests across all planned phases + fix integration flakiness ...

- Phase 3: 19 API route integration tests (health, agents, sessions, messages)
- Phase 3: 7 WebSocket integration tests (connect, send, replay, invalid, stop)
- Phase 4: 9 agent tests (_check_context_size, _iter_stream_guarded)
- Phase 4: 5 planning tests (_parse_plan_steps)
- Phase 5: 22 tool tests (filesystem 13, code_exec 5, terminal 4)
- Fix flaky integration tests by patching module-level singletons
  (_session_store, _registries, _workers) instead of getter functions,
  because FastAPI Depends() captures the original function at import time.
- Update docs/testing.md coverage table (150 total tests)

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