ackhandler: simplify packet number generation

[marten-seemann]

No functional change expected.

[Copilot]

Pull Request Overview

This PR replaces the old PeekPacketNumber/PopPacketNumber calls with a unified NextPacketNumber API across the packet packer and sent-packet handler, simplifying packet number generation without changing behavior.

• Swap PeekPacketNumber + PopPacketNumber for a single NextPacketNumber method.
• Update mocks and interfaces to reflect the new API.
• Refactor the sent-packet handler to track and issue packet numbers internally.

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packet_packer_test.go	Remove PopPacketNumber calls and leave only PeekPacketNumber (now needs updating)
packet_packer.go	Replace peek/pop with NextPacketNumber in packet generation
internal/mocks/ackhandler/sent_packet_handler.go	Update mock generation to support NextPacketNumber
internal/ackhandler/sent_packet_handler.go	Refactor handler to use NextPacketNumber and track next numbers
internal/ackhandler/interfaces.go	Change interface to expose NextPacketNumber only
connection.go	Switch to calling NextPacketNumber on version negotiation

Comments suppressed due to low confidence (2)

packet_packer_test.go:135

• After switching the interface to NextPacketNumber, tests must mock NextPacketNumber(...) instead of PeekPacketNumber(...) to avoid compilation failures and ensure correct expectations.

tp.pnManager.EXPECT().PeekPacketNumber(protocol.EncryptionInitial).Return(protocol.PacketNumber(0x24), protocol.PacketNumberLen3)

internal/ackhandler/sent_packet_handler.go:63

• [nitpick] The abbreviation PNG is ambiguous; consider renaming appDataPNG to appDataPacketNumberGenerator for greater clarity.

appDataPNG       *skippingPacketNumberGenerator

[Copilot]

Update the interface documentation comment to reflect removal of PeekPacketNumber/PopPacketNumber and explain the semantics of NextPacketNumber.

[codecov]

Codecov Report

Attention: Patch coverage is 87.03704% with 7 lines in your changes missing coverage. Please review.

Project coverage is 84.02%. Comparing base (7ca7a97) to head (42b2d7c).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/ackhandler/sent_packet_handler.go	82.05%	4 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5191      +/-   ##
==========================================
+ Coverage   84.00%   84.02%   +0.02%     
==========================================
  Files         152      152              
  Lines       17350    17350              
==========================================
+ Hits        14574    14578       +4     
+ Misses       2216     2212       -4     
  Partials      560      560              

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