Phase 6: strip signature-restating docstrings; correct README/SETUP

- Collapsed Args:/Returns:/Raises: blocks that only restated the
  signature (364 lines): tektronix_base 48% -> ~20% doc density,
  helios_laser and uc480_camera likewise. Only docstrings whose entire
  body was those sections were touched.
- Preserved verbatim the comments that carry hardware knowledge the code
  can't express: uc480's USB split-transaction contention note (with its
  measured fps), the IS_ALLOW_STARTER_FW_UPLOAD segfault explanation, the
  QImage-copy rationale, and tektronix's NUMFRAMESACQuired warning.
- README: project structure, quick start, and every usage example now
  describe code that exists (they referenced hardware/bbd202.py,
  CoherentHOPSLaser, get_curve_binary, and 'python -m scanengine.app',
  none of which do). Added a headless-scan example and a read-a-scan-file
  example, since reuse without the GUI is the point of the refactor.
- SETUP: structure section defers to README instead of keeping a second
  stale copy; documents the vendored uEye SDK and the Genesis quarantine.
- ruff is now clean repo-wide: fixed the remaining raise-from, unused
  loop variables, placeholder f-strings, and a non-strict zip; the
  widget-layout semicolon idiom is an explicit config ignore rather than
  22 standing warnings.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

t3r_control_panel.py

@@ -643,7 +643,7 @@ class T3RControlPanel(QDialog):
         self.conn_lbl.setText("opening…")
         self.connect_btn.setText("Disconnect")
         self.port_combo.setEnabled(False)
-        self._log(f"Port opened, sending PING…", "evt")
+        self._log("Port opened, sending PING…", "evt")
 
     def _on_handshake_ok(self, proto_ver: int, fw_ver: int, num_ch: int):
         self.conn_lbl.setText("connected")