fix(startup): preserve matching portable Run entries

[devseviq]

Saving startup preferences replaced an existing environment-based HKCU Run registration with an absolute path. Preserve a REG_EXPAND_SZ command when it expands to the exact quoted executable for the current installation, using a case-insensitive comparison. Stale paths, unresolved tokens, extra arguments, and non-expandable entries still receive the current command.

Adds nine regression cases using disposable registry keys and process-scoped environment variables, including disabling startup and a missing executable.

Validation on current develop:

• Whitespace and style checks passed for both changed files.
• scripts/pre-commit-check.sh passed: Release build, 1,436 core tests passed (2 existing skips), and 143 monitor tests passed.
• Independent source review found no issues.