[feat] Add locale preference to client-raycast

[ThreeLight2000]

Motivation

Raycast users may run Raycast and Chrome in English while preferring Context OS in Korean. client-chrome now supports an explicit locale preference, and client-raycast should offer the same behavior through Raycast Extension Preferences.

Scope

• Add an Auto / 한국어 / English language preference to the Raycast extension manifest.
• Default to Auto using the Raycast runtime locale, with explicit preference override.
• Localize command UI, toasts, dates, and copy/export text in client-raycast.
• Keep Raycast manifest command metadata in English because it is platform metadata.
• Apply the preference on the next command invocation, using Raycast preference storage instead of custom storage.

Acceptance criteria

• Auto, Korean, and English preferences resolve correctly.
• Explicit Korean works while Raycast/Chrome remain in English.
• Preference is shared by all Raycast commands through getPreferenceValues.
• Invalid or missing values fall back to Auto.
• Command UI, toasts, dates, and copy/export output use the selected locale.
• Existing client-raycast lint, build, and tests pass.

Verification plan

• Add locale resolution and translation tests.
• Run client-raycast lint, build, and relevant tests.
• Verify the imported extension with Raycast after build per package workflow.

[ThreeLight2000]

Implementation started on branch codex/3-client-raycast-language-preference. Using Raycast Extension Preferences for Auto / 한국어 / English, with locale-aware command UI and no custom persistence layer.

[ThreeLight2000]

Implementation is complete in PR #4. Added Raycast Extension Preferences language selection (Auto / 한국어 / English), localized command UI, dates, toasts, and Context export output. Lint, typecheck, build, and tests pass. Manual Raycast import and UI verification remain required after importing apps/client-raycast/dist.