Reach Settings/Profile from the pause menu, with a way back

The pause menu (Escape during a question/CCS/flashcards run) only had
Resume/UI Sounds/Exit Run/Log Out. Settings already has an equivalent
"Interface sounds" toggle, so drop the duplicate from the pause menu.
More importantly, "player" and "ccs_player" hide the entire app shell
(header + sidebar), so there was no way to reach Settings or Profile
at all mid-session - add Profile/Settings buttons to the pause menu to
close that gap.

Navigating there follows the existing return_screen payload
convention (already used by simulation_history/results/review) rather
than inventing new navigation infrastructure: _navigate_from_pause()
remembers current_screen_name and passes it through show_screen's
payload. Both screens show a "Back to session" button when that's
set, and hide it otherwise (including on ordinary non-paused visits).

show_screen() unconditionally resumes the question timer via
_close_app_menu() as a side effect of any navigation, so
_navigate_from_pause() re-pauses it immediately when leaving "player" -
the timer then resumes for real, for free, when the user actually
returns via show_screen(return_screen).

progress_profile.gd rebuilds its whole child tree on every theme
toggle (_rebuild -> _build), which would otherwise wipe the button's
visibility - added _refresh_back_to_session_visibility(), called both
after _build() and from on_show(), so it survives a theme change while
paused.

Flipped tests/web_responsive_test.gd's assertion, which previously
required the pause menu NOT to have a Profile button.

Verified end-to-end headlessly: opening the pause menu from a live
"player" session, navigating to Settings and Profile, confirming
current_question_pause_started_at is correctly paused while away and
resumed on return, confirming the back-to-session button appears only
when reached via pause (not on ordinary nav), and confirming it
survives a dark/light theme toggle on the Profile screen.

scripts/ui/settings_screen.gd

@@ -13,6 +13,8 @@ var followups_toggle: CheckButton
 var question_scale_value_label: Label
 var ccs_scale_value_label: Label
 var core_block_size_value_label: Label
+var return_screen := ""
+var back_to_session_button: Button
 
 
 func _ready() -> void:
@@ -39,6 +41,17 @@ func _ready() -> void:
 	subtitle.add_theme_color_override("font_color", Brand.SLATE)
 	add_child(subtitle)
 
+	back_to_session_button = Button.new()
+	back_to_session_button.text = "Back to session"
+	back_to_session_button.custom_minimum_size = Vector2(0, 44)
+	back_to_session_button.size_flags_horizontal = Control.SIZE_SHRINK_BEGIN
+	back_to_session_button.add_theme_stylebox_override("normal", Brand.gradient_button_box())
+	back_to_session_button.add_theme_color_override("font_color", Color.WHITE)
+	back_to_session_button.visible = false
+	UISoundService.set_button_sound(back_to_session_button, "back")
+	back_to_session_button.pressed.connect(_return_to_session)
+	add_child(back_to_session_button)
+
 	var panel := PanelContainer.new()
 	panel.custom_minimum_size = Vector2(520, 0)
 	panel.size_flags_horizontal = Control.SIZE_SHRINK_BEGIN
@@ -98,7 +111,10 @@ func _ready() -> void:
 	_refresh_text_scale_labels()
 
 
-func on_show(_payload: Variant = null) -> void:
+func on_show(payload: Variant = null) -> void:
+	var wrapper: Dictionary = payload if typeof(payload) == TYPE_DICTIONARY else {}
+	return_screen = str(wrapper.get("return_screen", ""))
+	back_to_session_button.visible = not return_screen.is_empty()
 	theme_toggle.set_pressed_no_signal(UIThemeService.is_dark_mode())
 	sound_toggle.set_pressed_no_signal(UISoundService.are_sounds_enabled())
 	followups_toggle.set_pressed_no_signal(BlockSessionService.show_review_followups)
@@ -209,6 +225,12 @@ func _open_legal_document(kind: String) -> void:
 	main.open_legal_document(kind)
 
 
+func _return_to_session() -> void:
+	if return_screen.is_empty():
+		return
+	main.show_screen(return_screen)
+
+
 func _on_theme_changed(is_dark: bool) -> void:
 	theme_toggle.set_pressed_no_signal(is_dark)
 	var panel := theme_toggle.get_parent().get_parent() as PanelContainer