esp: improve oseq overflow handling.

[philljj]

Description

Improve ESP oseq overflow handling.

Add unit test to check overflow.

Fixes F-696.

[Copilot]

Pull request overview

This PR improves ESP outbound sequence-number (oseq) overflow handling and adds a unit test to validate the overflow behavior, addressing F-696.

Changes:

• Initialize ESP outbound replay sequence (oseq) to 0 so the first transmitted sequence becomes 1 after pre-increment.
• Pre-increment oseq during esp_transport_wrap() and reject the wrap-around-to-0 case.
• Add a unit test that drives oseq to ESP_MAX_32_SEQ and asserts the overflow wrap is rejected.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
wolfesp.h	Adjusts replay initialization to start outbound sequence counter at 0.
src/wolfesp.c	Updates outbound sequence increment/overflow check in ESP transport wrapping.
src/test/unit/unit_esp.c	Adds and registers a unit test covering oseq overflow rejection.

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[Copilot]

Pull request overview

Improves ESP outbound sequence number (oseq) overflow handling to prevent wrap-around/reuse, and adds a unit test to validate the behavior (Fixes F-696).

Changes:

• Initialize outbound replay.oseq to 0 so the first transmitted ESP sequence is still 1 after the pre-increment behavior.
• Detect oseq overflow during esp_transport_wrap() and reject further transmissions by latching oseq at max and returning -1.
• Add a unit test that drives oseq to the overflow boundary and asserts repeated rejection after overflow.

Reviewed changes

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

File	Description
wolfesp.h	Adjusts replay initialization so outbound oseq starts at 0 (works with pre-increment send semantics).
src/wolfesp.c	Moves oseq increment before writing SEQ and adds overflow detection that prevents wrap-around reuse.
src/test/unit/unit_esp.c	Adds test_replay_overflow to verify overflow is detected and remains rejected on subsequent wraps.

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