fix: timer loading — zero duration, start failure, and keepScreenOn sync

[nbucic]

Root cause

When a program has no phases:

• Program::totalDuration() returns 0 → programTotalDuration = 0
• TimerRunner::start() throws RuntimeException("Program has no phases.") — this exception silently rolls back the Livewire response, so the UI never updates and the Start button appears to do nothing

This can happen when a user creates a program and navigates to the timer without adding any phases.

Changes

TimerScreen::start() — guard against empty phases

Instead of propagating an exception from TimerRunner::start(), the action now returns early when phases are empty. State is left untouched and the blade renders the "no phases" notice.

timer-screen.blade.php — no-phases notice

When the timer is idle and $phases is empty, the Start button is replaced with an amber warning: "No phases — edit this program to add at least one phase before starting." The Edit button in the secondary row is still shown so the user can fix the program immediately.

ProgramEditor::totalDuration() — match timer behaviour

The editor's preview summed every phase's cooldown, including the last phase. But the timer skips the last phase's cooldown (goes straight to COMPLETED after the final rep). This made the preview total higher than the actual run duration for any program with a last-phase cooldown. Fixed to subtract the last phase's cooldown, matching Program::totalDuration().

TimerScreen::loadProgram() / requestSettings() — forward keepScreenOn

Both methods dispatch settingsLoaded to sync JS audio state, but neither included keepScreenOn. The fix/tts-wakelock-caching commit added a settingsLoaded JS handler that reads keepScreenOn to gate wake-lock acquisition. Without it, the wake lock could be stuck in the wrong state whenever a program was loaded or settings were refreshed. Both dispatches now include keepScreenOn: $this->keepScreenOn.

Test plan

• Open a program that has no phases → timer screen shows amber "No phases" notice, no Start button
• Edit the same program, add a phase, save → redirected to timer, Start button visible, timer starts normally
• Start a program with phases → 5-second PREPARE countdown plays, timer counts down correctly
• Open program editor on a program whose last phase has a non-zero cooldown → preview total matches the actual timer run (cooldown excluded)
• Open settings, toggle Keep Screen On, save → confirm the timer respects the new value on next program load

https://claude.ai/code/session_018ofANSCtBHs5P8rvvJ9Mh3

[nbucic]

@copilot resolve the merge conflicts in this pull request