docs: 2000-2124 is the SPA extended range, not SPH

Every register the reference lists in that block is labelled SPA, and the #360
reporter's three-phase SPH-layout device answers none of it. The range summary
said SPH extended, which points anyone checking it at the wrong family.

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

Author: 0xAHA

docs/developer/protocol-database.md

@@ -41,7 +41,7 @@ Inverter startup detection:
 | 0–124 | V1.39 | Base holding and input registers (all models) |
 | 875–999 | V1.39 | WIT commercial registers |
 | 1000–1124 | V1.39 | SPH/SPA storage control |
-| 2000–2124 | V1.39 | SPH extended |
+| 2000–2124 | V1.39 | SPA extended (single-phase AC storage) |
 | 3000–3374 | V1.39 | MIN/MOD extended data |
 | 8000–8139 | V1.39 | WIT battery registers |
 | 30000–30099 | VPP | Device ID, rated parameters |