feat(update): disable real updates in make run dev builds

[BlackHole1]

A make run build is always versioned 0.0.0-development, so every update check against the shipped production feed would "find" the newest stable release and could download and install it over the build under test. Sparkle is therefore never started in a bare dev build: no scheduled check fires and the production feed is never contacted. A manual "Check for Updates…" stays available but surfaces a "disabled in development" notice instead.

The update lab (make update-test-*) is the one exception: it redirects the feed to a loopback server via LOCKIME_UPDATE_FEED, so the presence of that env var distinguishes the lab from a plain run and keeps its real download/install flow working. All new code is under #if DEBUG, leaving release builds unchanged.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 74c483af-6bd5-4f4e-98c2-69f137204b40

📥 Commits

Reviewing files that changed from the base of the PR and between e9834e8 and 53302ad.

📒 Files selected for processing (3)

• Sources/LockIME/AppState.swift
• Sources/LockIME/Localizable.xcstrings
• Sources/LockIME/Updates/UpdateController.swift

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Summary by CodeRabbit

• Chores
  • Improved development build messaging for update check handling, including informational alerts and localized guidance for testing workflows.

Walkthrough

This PR adds development-build update isolation: when the LOCKIME_UPDATE_FEED environment variable is empty in DEBUG builds, automatic updates are disabled to prevent dev builds from contacting the production feed. A new UpdateCheckOutcome.disabledInDevelopment case signals this state. The controller skips Sparkle initialization but allows manual checks to surface a localized "Development build" alert that directs developers to use lab workflow commands to test the update flow.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The pull request title follows the required format and clearly describes the main change: disabling real updates in development builds.
Description check	✅ Passed	The pull request description is directly related to the changeset and provides relevant context about why updates are disabled in development builds.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch disable-update-dev

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