Allocate APS sequence numbers directly

[puddly]

Flagged in zigpy/ziggurat#56.

APS sequence numbers should be decoupled from the ZCL TSN that zigpy is (erroneously) passing through to the radio library. No other radio library actually passes through the APS sequence number so this doesn't really affect production networks.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (c92f735) to head (b2d72cd).

Additional details and impacted files

@@            Coverage Diff            @@
##               dev        #6   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         7           
  Lines         1681      1687    +6     
=========================================
+ Hits          1681      1687    +6     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

This PR decouples APS sequence number allocation from the ZCL transaction sequence number (TSN) previously propagated via packet.tsn, aligning behavior with other radio libraries and addressing zigpy/ziggurat#56.

Changes:

• Introduces an internal APS sequence counter in ControllerApplication and uses it for all outgoing unicast/broadcast/groupcast frames.
• Allocates APS sequence numbers at send-time (within the concurrency limiter) to better reflect the order frames are sent to the server.
• Updates application and legacy tests to assert the new APS sequence numbering behavior (starting at 1).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
zigpy_ziggurat/zigbee/application.py	Adds an internal APS sequence counter and uses it instead of packet.tsn when building outbound send requests.
tests/test_legacy.py	Updates legacy-protocol send assertions to match the new internally allocated APS sequence values.
tests/test_application.py	Updates packet helpers and send tests to stop relying on tsn for APS sequence and to assert the new counter behavior.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.