Fix packet-pool slot leak in canned message destination picker

[thebentern]

Summary

CannedMessageModule::updateDestinationSelectionList() allocated a meshtastic_MeshPacket via allocDataPacket() that was never sent nor released, permanently consuming one slot from packetPool on every rebuild of the destination-selection picker.

meshtastic_MeshPacket *p = allocDataPacket();
p->pki_encrypted = true;
p->channel = 0;
// ...p is never used again, never sent, never released

Impact

• Non-PSRAM targets: packetPool is a static 70-slot BSS pool (Router.cpp:57-66). Repeated use of the destination picker steadily drains it and eventually blocks all packet allocation, causing TX/RX failures.
• PSRAM / portduino targets: packetPool uses MemoryDynamic, so this is a true heap leak of ~424 B per rebuild.

The picker is rebuilt on entry to destination selection, on every search keystroke, and whenever the node list changes, so the leak accumulates quickly in normal use.

Root cause

The three lines were a copy/paste artifact of the legitimate PKI setup in sendText() (introduced in #8182, "Multi message storage"). In sendText() the allocated packet is populated and handed to service->sendToMesh(); here it was pasted into a function that only builds a UI list and has nothing to send.

Fix

Remove the dead allocation. No other code in the function references p, so there is no behavior change beyond eliminating the leak. allocDataPacket()'s only side effect is bumping the monotonic packet-ID counter, which is harmless to skip since nothing was ever transmitted.

Testing

• Native test suite: 602/602 passing (./bin/test-native-docker.sh)
• trunk fmt: clean

Summary by CodeRabbit

• Refactor
  • Simplified internal destination-selection processing without changing observable behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 89384332-5483-49a1-85e4-28734ab1e903

📥 Commits

Reviewing files that changed from the base of the PR and between deea7be and 64d23a8.

📒 Files selected for processing (1)

• src/modules/CannedMessageModule.cpp

💤 Files with no reviewable changes (1)

• src/modules/CannedMessageModule.cpp

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📝 Walkthrough

Walkthrough

updateDestinationSelectionList() no longer allocates a meshtastic_MeshPacket or assigns its encryption and channel fields before populating active channels and adjusting selection indices.

Changes

Destination selection cleanup

Layer / File(s)	Summary
Remove unused packet setup src/modules/CannedMessageModule.cpp	Removes the unused mesh packet allocation and pki_encrypted/channel assignments from destination selection updates.

Estimated code review effort: 1 (Trivial) | ~2 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the core change: removing a packet-pool leak in the canned message destination picker.
Description check	✅ Passed	The description covers summary, impact, root cause, fix, and testing; only the template attestation section is omitted.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/funny-panini-4cbeb3

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