fix(trezor-client): send empty passphrase for standard wallets

[ifdario]

Fixes #7033

handle_interaction incorrectly handles PassphraseRequest for standard wallets (no passphrase configured).

When on_device() returns false, the current code calls req.ack(!on_device) which sets on_device = true in the PassphraseAck, causing the Trezor to prompt for passphrase entry on the device even when none is configured.

The fix sends an empty passphrase string via ack_passphrase(String::new()) when on_device() is false, which is the correct protocol response for standard (non-hidden) wallets.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 67cce5fb-60e5-4450-8c1a-67278c879efe

📥 Commits

Reviewing files that changed from the base of the PR and between a3bc309 and 99b8fcb.

📒 Files selected for processing (1)

• rust/trezor-client/src/client/common.rs

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Walkthrough

This PR fixes a bug in the Trezor client's interaction handler. The handle_interaction function previously called req.ack(!on_device) for all PassphraseRequest cases, which incorrectly sent on_device=true when the request had on_device=false. The fix adds explicit branching: when the device should handle passphrase entry, it calls req.ack(true); otherwise it calls req.ack_passphrase(String::new()) to provide an empty passphrase string. The resulting response is then recursively handled.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: fixing passphrase handling for standard wallets in the trezor-client.
Description check	✅ Passed	The description clearly explains the bug, root cause, and the fix with relevant code context and protocol details.
Linked Issues check	✅ Passed	The code changes directly address issue #7033 requirements: branching on on_device(), calling ack(true) when true, and ack_passphrase(String::new()) when false.
Out of Scope Changes check	✅ Passed	All changes are scoped to fixing PassphraseRequest handling in handle_interaction, directly addressing the linked issue #7033 with no extraneous modifications.

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✨ Finishing Touches

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