[Critical] Dead code references non-existent WhisperPluginFactory

[Coldaine]

Summary

plugin_manager.rs contains dead code that references WhisperPluginFactory which does not exist in the codebase. This indicates incomplete cleanup from previous refactoring.

Locations

• crates/app/src/stt/plugin_manager.rs:572-573
• crates/app/src/stt/plugin_manager.rs:1522-1537

Impact

• Code will fail to compile if these paths are exercised
• Confusing for developers
• Indicates other incomplete cleanup may exist

Recommended Fix

1. Remove all WhisperPluginFactory references
2. Audit for other dead references to removed plugins
3. Verify all feature flag paths compile

Related

• Agent 4 (Plugin Manager) review finding
• Stub plugins were removed but references remain
• PR chore(stt): remove stub STT plugin files #282 removes stub files but not internal references

Priority

P0 - Fix this week (simple fix)}