Add support for Simplicity SDK 2025.12.3

[puddly]

No new commands that we use but I'm adding these for completeness.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.54%. Comparing base (4ee82da) to head (85408d7).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #725   +/-   ##
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  Coverage   99.54%   99.54%           
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  Files          61       61           
  Lines        4147     4181   +34     
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+ Hits         4128     4162   +34     
  Misses         19       19           

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[zigpy-review-bot]

LGTM. I independently verified every frame ID and struct layout in this PR against the actual simplicity-sdk/2025.12.3 headers (installed via slt), and cross-checked the pre-2025.12 items against zigbee-herdsman. Everything matches exactly.

Verified against the 2025.12.3 SDK source (ezsp-enum.h, stack/include/sl_zigbee_dhc.h):

• All DHC PA frame IDs 0x0152–0x0169 ✅ — including the out-of-order WRITE_RSSI_OFFSET = 0x015F and the 0x0165 gap (READ_PA_VERSION = 0x0164 → READ_PA_SIGNATURE = 0x0166; there is no writePaVersion, PA version is read-only).
• All five DHC structs match field-for-field (widths + order): descriptor, curve segment, curve, table, metadata. The maxPowerLevel camelCase field amid otherwise snake_case names is faithful — the SDK header itself notes field name 'maxPowerLevel' must match YAML for generated marshal code.
• setPendingNetworkUpdateChannel = 0x003D ✅ — confirmed; the slot was genuinely reclaimed (getFirstBeacon no longer exists in the 2025.12.3 SDK).
• radioSetSchedulerPriorities = 0x012B is absent from 2025.12.3's ezsp-enum.h (only GET = 0x012A and SLIPTIME 0x012C/0x012D remain), confirming the in-code note that it was dropped in 2025.12.2 without a version bump. The v14 (3-field) → v16+ (5-field) split is correct; sl_802154_radio_priorities_t matches the header exactly.

Full test suite passes locally (424) and the new structs round-trip at the expected packed sizes. One optional, non-blocking note inline.

[zigpy-review-bot]

Optional / non-blocking: since the 2025.12.3 SDK reclaimed 0x003D for this command, the inherited getFirstBeacon (at 0x003D since v7) is now a dead opcode in v18 firmware. Harmless as-is — setPendingNetworkUpdateChannel is inserted later so it wins COMMANDS_BY_ID[0x003D], and both stay callable by name — and it mirrors the existing v17 pattern (gpProxyTableRemoveEntry/gpClearProxyTable reusing 0x5D/0x5F). But if you'd like v18 to reflect the firmware exactly, you could drop getFirstBeacon here.