fix(cli): implement Windows CLI registration via the user PATH

[DocInTardis]

Summary

• implement CLI registration and unregistration on Windows by updating the user-scoped Path environment variable

Changes

• add electron/windows-cli-path.ts helpers for PATH parsing, normalization, deduplication, and removal
• implement Windows branches in isCliRegistered(), registerCli(), and unregisterCli()
• use PowerShell to read/write the user PATH entry
• keep the existing macOS and Linux registration flows unchanged
• add focused regression tests for case-insensitive and slash-insensitive PATH handling

Testing

• node --experimental-strip-types --test tests/windows-cli-path.test.ts

Notes

• the updated PATH is user-scoped, so newly opened terminals should pick it up after registration

Closes #34

[blueberrycongee]

Superseded by newer PR. Closing duplicate.

[blueberrycongee]

Reopening: this Windows CLI PATH registration has no equivalent in #80-96 range. Unique contribution.