revert: "fix(callbacks/v2): OnTimeoutPacket blocked by UnmarshalPacketData error (backport #8856) (#8911)"

[srdtrk]

This reverts commit 84c5bad. Since it was state machine breaking, and therefore, has to be in a minor release.

Description

closes: #XXXX

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Linked to GitHub issue with discussion and accepted design, OR link to spec that describes this work.
• Include changelog entry when appropriate (e.g. chores should be omitted from changelog).
• Wrote unit and integration tests if relevant.
• Updated documentation (docs/) if anything is changed.
• Added godoc comments if relevant.
• Self-reviewed Files changed in the GitHub PR explorer.
• Provide a conventional commit message to follow the repository standards.

[greptile-apps]

Greptile Summary

This PR reverts the backport of #8911 (which fixed OnTimeoutPacket being blocked by UnmarshalPacketData errors in callbacks/v2) because the fix is state-machine breaking and must ship in a minor release rather than a patch. The middleware is restored to returning err on unmarshal failure, and the v10.5.2 changelog section is removed.

Confidence Score: 5/5

Safe to merge — the revert logic is correct; only a minor CHANGELOG formatting nit remains.

The middleware change is a clean revert with no logic errors. The only finding is a P2 cosmetic issue (missing * bullet in CHANGELOG), which does not affect correctness or release safety.

CHANGELOG.md — missing bullet prefix on the v10.5.1 entry

Important Files Changed

Filename	Overview
CHANGELOG.md	Removes v10.5.2 section (reverted) but accidentally strips the * bullet prefix from the v10.5.1 transfer entry
modules/apps/callbacks/v2/ibc_middleware.go	Reverts OnTimeoutPacket from returning nil (non-blocking) back to returning err when UnmarshalPacketData fails; also restores the removed comment

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[OnTimeoutPacket called] --> B[im.app.OnTimeoutPacket]
    B -->|err != nil| C[return err]
    B -->|nil| D[im.app.UnmarshalPacketData]
    D -->|err != nil - BEFORE revert| E["return nil (non-blocking)"]
    D -->|err != nil - AFTER revert| F["return err (blocking)"]
    D -->|nil| G[GetCallbackData]
    G -->|not a callback packet| H[return nil]
    G -->|callback packet| I[Execute callback]
    I --> J[return result]

    style E fill:#f9f,stroke:#333,stroke-dasharray: 5 5
    style F fill:#bbf,stroke:#333

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Comments Outside Diff (1)

1. CHANGELOG.md, line 41 (link)

   Missing bullet prefix on v10.5.1 entry

   The revert accidentally dropped the * bullet prefix from the v10.5.1 transfer entry, inconsistent with every other entry in the file (e.g. v10.5.0, v10.4.0 all use * ).

_{Reviews (1): Last reviewed commit: "docs: keep style imp" | Re-trigger Greptile}

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release/v10.5.x@84c5bad). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
modules/apps/callbacks/v2/ibc_middleware.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##             release/v10.5.x    #8912   +/-   ##
==================================================
  Coverage                   ?   62.53%           
==================================================
  Files                      ?      288           
  Lines                      ?    20811           
  Branches                   ?        0           
==================================================
  Hits                       ?    13015           
  Misses                     ?     7230           
  Partials                   ?      566           

Flag	Coverage Δ
08-wasm	66.28% <ø> (?)
e2e	1.18% <ø> (?)
ibc-go	68.95% <0.00%> (?)

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