Add reference documentation for three new TUI features:
- docs/reference/tui_shell_safety.md: Full reference for the shell danger
detection subsystem (DangerousPatternDetector, ShellDangerLevel,
DangerousPattern, DangerousCommandWarning, DEFAULT_PATTERNS registry).
Covers all built-in patterns across CRITICAL/HIGH/MEDIUM/LOW levels,
usage examples, and custom pattern extension.
- docs/reference/tui_permission_question.md: Full reference for the inline
PermissionQuestionWidget (issue #997). Documents InlinePermissionQuestion,
PermissionRequestType, PermissionDecision, render_permission_question(),
PermissionDecisionEvent, and PermissionQuestionWidget with key bindings
and usage examples.
- docs/reference/tui.md: Extended with First-Run Experience section
(ActorSelectionOverlay, first_run helpers), Inline Permission Questions
section, shell danger detection note in Shell Mode, updated module table,
and links to new reference pages.
