fix: Harmonize timeout exceptions to OSError per convention #44.

[nedseb]

Context

The auto-trigger convention (#44) specifies that timeout errors in _ensure_data() and related polling methods should raise OSError. Most drivers follow this:

Driver	Timeout exception	Follows #44
HTS221	OSError	✅
LIS2MDL	OSError	✅
VL53L1X	OSError	✅
APDS9960	OSError	✅
ISM330DL	OSError	✅
BME280	OSError	✅ (fixed in PR #318)
WSEN-PADS	WSENPADSTimeout	❌
WSEN-HIDS	WSENHIDSTimeoutError	❌

Tasks

• lib/wsen-pads/wsen_pads/device.py: change raise WSENPADSTimeout(...) to raise OSError(...) in _ensure_data() and _wait_boot()
• lib/wsen-hids/wsen_hids/device.py: change raise WSENHIDSTimeoutError(...) to raise OSError(...) in one-shot timeout paths
• Update or remove unused timeout exception classes from exceptions.py if no longer referenced
• Verify tests still pass after changes

Reference

• drivers: Ensure read methods auto-trigger conversion in power-down mode. #44 — auto-trigger convention (specifies OSError)