permissions: remove broken client-side gate; add backend design doc ...

The terminal-TUI permission gate was a race: _execute_tools_with_sink
emits ToolStarted and starts the tool on the backend immediately, so by
the time the client dialog appeared the destructive action had already
run -- 'deny' could only stop the session, not un-execute the tool. It
also existed only in the terminal TUI (webclient/android had nothing),
and the system-prompt 'Strict Confirmation' nudge was an unreliable
duplicate.

Remove the broken machinery for a clean slate and plan the real
replacement from zero:

- delete clients/terminal/tui/permissions.py, screens/permission_dialog.py
  and their tests
- strip tui_app.py (engine, _deny_tool, _show_permission_dialog,
  _confirm_shell_command, _stop_session_worker, on_permission_request,
  tool_started gate) and the PermissionRequest TUI event; !cmd now runs
  directly (user-typed, no agent gate)
- drop the 'Strict Confirmation' prompt rule from navi_code/developer/
  tool_developer
- add docs/permissions.md: authoritative backend gate design (engine +
  registry + event + endpoint + agent gate + postgres policy + global
  rules config, sub-agents gated) -- design only, not yet implemented
- update docs/index.md, navi_code_cli.md, profiles.md, testing.md

Until Phase 1 lands there is no destructive-action confirmation -- a
conscious period without the false security of the old race-gate.

Navi Code TUI: remove sessions table from right column ...

Drop the SessionsPanel widget and all dead code wired to it (handlers,
broadcast helper, session-list events, _refresh_sessions worker). The
/new, /sessions, /switch commands are preserved — they already operate
via app.attach_session / chat output rather than the panel.

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

Navi Code TUI: Phase 5.2 — SessionsPanel, /export, integration tests ...

- Add right-side SessionsPanel widget (DataTable) listing server sessions.
- Wire SessionsPanel into TUI layout and session selection flow.
- Add SessionSelected / SessionListUpdated events and refresh logic.
- Implement /export slash command: markdown rendering + $EDITOR.
- Update /new, /sessions, /switch, /profile to use session_id/name/preview.
- Add integration tests for SessionsPanel and /export; update layout test.
- Update docs/navi_code_cli.md with new panel and command.

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

Navi Code TUI: fix Phase 4 review critical/medium issues ...

- PermissionEngine: always-deny returns None via check(); is_always_deny() exposed for explicit rejection; default rules for code_exec/ssh_exec/shell; extract_target() made public.
- ShellRunner: set ShellResult.truncated when output is actually truncated.
- File refs: restrict paths to base_dir/home, block sensitive files/dirs, skip binary, support glob brackets, shared guess_language.
- Permission dialog: deny now renders synthetic tool_call before stopping; shell ! commands require permission with always-allow/deny persistence.
- Tests: add permission tests, fix file_refs/shell tests, add __init__.py to fix pytest name collisions, update websocket integration for AgentSessionOrchestrator.

504 passed, 1 skipped. Ruff clean.

Signed-off-by: Eugene Sukhodolskiy <eugene.sukhodolskiy@gmail.com>

Navi Code: Phase 3 — Textual TUI skeleton (OpenCode-style) ...

- Add clients/terminal/tui package with micro-architecture:
  - events, context, chat_model, ws_bridge, permissions engine.
  - widgets: ChatPanel, StatusPanel, InputBox.
  - renderers: user/assistant messages, thinking, tool calls, errors,
    markdown, plain — registry-based and extensible.
  - slash commands: /help, /new, /sessions, /switch, /profile, /thinking,
    /compact, /quit — registry-based and extensible.
- Wire navi-code to launch TUI by default; keep click-CLI via --raw.
- Add textual>=0.70 dependency.
- Add TUI smoke tests via Textual Pilot.
- Add docs/plan_navi_code_tui.md with full Phase 4/5 roadmap.

Tests: 463 passed, 1 skipped (excluded unrelated websocket test).

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