feat: add actionable kDrive contextual actions

[OpenCow42]

Summary

• add single-item favorite, duplicate, and trash-restore File Provider actions
• add a File Provider UI extension for share-link management and version history
• persist favorite metadata, correct trash/offline item behavior, and record sanitized action activity
• add per-drive Show in Finder/Files and Sync Now controls
• restore shared app and extension schemes for reproducible Xcode builds
• document the v0.3 architecture, API mapping, persistence, and lifecycle behavior

Validation

• iOS Simulator 26.5 (iPhone 17): 127 Swift tests and 6 UI tests passed
• visionOS Simulator 26.5 (Apple Vision Pro): 127 Swift tests and 4 UI tests passed
• macOS: app build and complete build-for-testing passed
• snapshot persistence cleanup suite: 9 tests passed without SQLite vnode warnings
• extension plists, activation predicates, entitlements, embedded extension artifacts, and version 0.3.0 verified
• potassiumChannel remains resolved at 0.2.0
• sensitive-value logging scan and git diff integrity checks passed

macOS test runner note

On this machine, macOS XCTest execution stalls before any test starts in Xcode IDEInstallLocalMacWorker with “waiting for workers to materialize.” Compilation, linking, app launch, and build-for-testing all succeed; the same test suite passes on iOS and visionOS simulators.