Introduces a root Package.swift that compiles a subset of model code into
a CaffeineCore library so swift test can run automated unit tests without
touching the Xcode project. Adds two backend protocols that abstract the
system APIs that subsequent milestones will depend on:

- LaunchItemBackend wraps SMAppService.mainApp for login-item registration.
- PowerAssertionBackend wraps IOPMAssertionCreateWithDescription /
  IOPMAssertionRelease for sleep prevention.

Includes a smoke test exercising the default implementations.

Adds a new "Launch at Login" toggle in Preferences that registers the
app as a macOS login item via SMAppService.mainApp. The published state
mirrors the underlying SMAppService status so manual toggles in System
Settings flow back into the UI on next appearance.

Tests cover register/unregister wiring, the no-op-when-already-enabled
case, and recovery when the backend throws.

Adds an "Allow Mac to run with lid closed" preference. SleepPreventionManager
now holds up to three IOPMAssertions while active:
  - PreventUserIdleDisplaySleep (display does not dim from inactivity)
  - PreventUserIdleSystemSleep  (system does not idle-sleep — previously absent)
  - PreventSystemSleep          (only when the new flag is on, lets the Mac
                                 keep running with the lid closed on AC power)

The assertion timeout is bumped from 8 s to 30 s so the 10 s refresh always
overlaps; the previous values left a 2 s gap every cycle.

The manager accepts an injected PowerAssertionBackend so tests can verify
which assertion types are created. Toggling the flag while active applies
live without re-activating.

Integration smoke test in scripts/integration-test.sh launches the built
app with a debug env var, then verifies `pmset -g assertions` reflects the
expected types.

Adds zh-Hant.lproj/Localizable.strings (full translation) and appends the
three new preference strings — "Launch at Login", "Allow Mac to run with
lid closed", and the AC-power caveat — to every shipped locale (best-effort
native translations for de/es/fr/it/nl/pt/pt-BR/ru/uk; native review
welcome via follow-up PRs).

LocalizationTests parses each .strings file and asserts the full key set
is present, so future user-facing strings can't land without updating
every locale.

The README now describes this fork (bubbleee030/Caffeine) instead of the
upstream project's download page and support contact. Adds a tutorial for
the two new toggles, including a `pmset -g assertions` verification step,
a Languages section listing all 14 shipped locales, and a Building from
source section. The original FAQ entries are kept and the alternatives
question is updated to reflect that this fork now provides lid-close
parity with Amphetamine.

README.zh-Hant.md mirrors the English README with localized headings and
Taiwan-style vocabulary so Traditional-Chinese readers get the same
information without an English detour.

#1 SleepPreventionManager.refreshAssertions now creates the three new
   assertions before releasing the old IDs, so the kernel always sees at
   least one of each type during a refresh (swap-then-release, not
   release-then-create). The doc comment claimed overlap but the code
   left a microsecond gap. New testRefreshCreatesNewAssertionsBeforeReleasingOld
   pins the ordering via an operationLog on the test fake.

#2 NSWorkspace session observers now use the Combine publisher API with
   AnyCancellable, so they detach automatically when the manager
   deallocates. The previous selector-based addObserver retained the
   target forever — fine for the production singleton, but every test
   that constructed a SleepPreventionManager(backend:) leaked two
   observers. testManagerDeallocatesWhenOutOfScope proves the leak is
   fixed via a weak ref.

#3 LaunchAtLoginManager.setEnabled now logs the underlying error via
   os.Logger (subsystem net.domzilla.caffeine, visible in Console.app)
   and surfaces it on a public `lastError` property so the UI layer can
   present it to the user. refresh() still snaps the published isEnabled
   back to the backend truth, so a failed register visually pops the
   Toggle back to off. Two new tests cover lastError set on throw and
   cleared on next success.

#4 scripts/integration-test.sh replaces the fixed 3 s sleep with a
   poll_for_caffeine_assertions helper that retries pmset every second
   until Caffeine-owned assertions appear (default 30 s timeout,
   overridable via ASSERTION_POLL_TIMEOUT). Avoids flakiness on slow
   runners where SwiftUI initialization takes longer than 3 s.

#5 PreferencesView no longer writes CAAllowLidClose to UserDefaults twice.
   CaffeineViewModel.setAllowLidClose now only forwards the new flag to
   SleepPreventionManager; persistence is owned by PreferencesView's
   @AppStorage binding.

#6 SleepPreventionManager now releases its assertion IDs immediately when
   the user session resigns active, and re-engages immediately on become-
   active rather than waiting up to 10 s for the next timer tick. The old
   early-return in refreshAssertions left the manager's stored IDs in a
   stale state after the kernel timed them out at 30 s. Three new tests
   cover resign-releases, become-reengages, and become-while-inactive
   does nothing.

#7 CA_TEST_AUTOACTIVATE no longer writes to standard UserDefaults. The
   activate(...) function takes a new allowLidCloseOverride parameter so
   the test hook can drive a known state without mutating persistent
   preferences. The intentional early-return is documented in comments.

#8 LocalizationTests no longer relies on a single representative key
   ("Quit") to prove zh-Hant differs from zh-Hans. Asserts that at least
   half of all 31 user-facing values are non-identical across the two
   locales.

#9 About-dialog credits now point at github.com/bubbleee030/Caffeine
   instead of github.caffeine-app.net, in line with the README rewrite.
   Added a 2026 @bubbleee030 line to the copyright credits. Updated the
   source string in MenuBarController and the localized value in all 14
   .lproj/Localizable.strings files; LocalizationTests reflects the new
   key. No remaining caffeine-app.net references in the repo.

…d-close

Add Launch at Login + lid-close support, Traditional Chinese, automated tests