style: apply ruff lint fixes and formatting to figment modules

Fixes: unused imports, import sorting, unused variable, overly broad
exception type in test.

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

engine/layers.py

@@ -57,9 +57,7 @@ def render_message_overlay(
     else:
         msg_rows = msg_cache[1]
 
-    msg_rows = msg_gradient(
-        msg_rows, (time.monotonic() * config.GRAD_SPEED) % 1.0
-    )
+    msg_rows = msg_gradient(msg_rows, (time.monotonic() * config.GRAD_SPEED) % 1.0)
 
     elapsed_s = int(time.monotonic() - m_ts)
     remaining = max(0, config.MESSAGE_DISPLAY_SECS - elapsed_s)
@@ -353,8 +351,6 @@ def render_figment_overlay(
         if has_content:
             line_str = "".join(line_buf).rstrip()
             if line_str.strip():
-                overlay.append(
-                    f"\033[{scr_row};{center_col + 1}H{line_str}{RST}"
-                )
+                overlay.append(f"\033[{scr_row};{center_col + 1}H{line_str}{RST}")
 
     return overlay