TypeWhisper 1.7 preview: Swift 6.3 validation daily

This daily includes the dependency update from #1293 and the new plugin compatibility policy from #1294. It is the everyday-testing build before 1.7.0-rc1.

What's new since 1.6

• iCloud synchronization for History and Inbox, alongside a redesigned History interface with device grouping, filtering, and search. iCloud sync has already been tested; this build keeps it enabled.
• Transcribe files from Finder and use the optional Web Link plugin to transcribe web media.
• More workflow controls, including spoken submit, Inline Commands, and a choice of double Escape, single Escape, or immediate cancellation.
• Expanded plugin capabilities, including plugin pages and optional providers that use authenticated command-line tools.
• Improvements to Bluetooth recording startup, model restoration, cancellation, text insertion, and transcription recovery.

Changes being validated in this daily

• Build and release workflows now use Xcode 26.6 and Swift 6.3. App and SDK dependency constraints agree, including Hugging Face 0.10.1 and Jinja 2.5.0, with MLX Swift 0.31.6.
• Future plugin releases built from this source line require TypeWhisper 1.7.0 or newer. Existing published plugin binaries and historical registry entries remain available to compatible 1.6 hosts. This app release does not republish plugins.

Please test your usual dictation workflows, installed plugins, and iCloud synchronization on this build. Track findings and candidate validation in #1296. RC1 follows the everyday test.

This is a Daily-channel prerelease, available from GitHub and the Daily update channel. The stable channel and Homebrew stay on the stable release.