Before Submitting This PR

Please confirm you have done the following:

• I have searched existing issues and pull requests (including closed ones) to ensure this isn't a duplicate
• I have read CONTRIBUTING.md

If this is a feature or change that was previously closed/rejected:

• I have explained in the description below why this should be reconsidered
• I have gathered community feedback (link to discussion below)

Human Written Description

I noticed the microphone error normalization added in #945 was turning generic permission-denied errors into Windows-specific remediation text on every platform. This keeps the Windows guidance on Windows, but preserves the original error on macOS/Linux so users are not sent to the wrong OS settings.

Related Issues/Discussions

Follow-up to #945

Fixes #: n/a (no dedicated issue)
Discussion: none

Community Feedback

None yet.

Testing

• cd src-tauri && cargo test --lib

Screenshots/Videos (if applicable)

N/A

AI Assistance

• No AI was used in this PR
• AI was used (please describe below)

If AI was used:

• Tools used: Pi coding agent
• How extensively: Used to inspect the existing bug, make the small Rust change, add unit tests, run checks, and draft this PR body.