Fix "Restarting" screen stuck forever

[Copilot]

Description

The restart screen hangs indefinitely because pidof python* doesn't work — pidof doesn't support shell globs. The wildcard expands against the current directory (matching nothing), so kill receives no PID and the process is never terminated.

Fix: Replace unreliable pidof/ps+grep process lookup with os.getpid() and sys.executable:

# Before (broken — pidof doesn't support wildcards)
call("kill $(pidof python*) & python /opt/src/main.py", shell=True)

# After
pid = os.getpid()
python = shlex.quote(sys.executable)
call(f"kill {pid}; exec {python} /opt/src/main.py", shell=True)

Additional changes:

• Thread safety for tests: DoResetThread checks self.keep_running before executing kill. RestartView.run() stops the thread on exception. This prevents the now-functional kill from terminating the screenshot generator process (which exercises RestartView without mocking the thread).
• Shell hardening: shlex.quote() on sys.executable; & → ; so kill completes before exec.

No screenshot changes — ResetScreen UI is unchanged; only the background thread logic is fixed.

This pull request is categorized as a:

• New feature
• Bug fix
• Code refactor
• Documentation
• Other

Checklist

• I've run pytest and made sure all unit tests pass before sumbitting the PR

If you modified or added functionality/workflow, did you add new unit tests?

• No, I'm a fool
• Yes
• N/A

I have tested this PR on the following platforms/os:

• Raspberry Pi OS Manual Build
• SeedSigner OS on a Pi0/Pi0W board
• Other

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[Copilot]

Pull request overview

Fixes SeedSigner’s “Restarting” screen hanging indefinitely by replacing unreliable process lookup (pidof python* / ps|grep) with a deterministic restart strategy based on the current PID and Python executable.

Changes:

• Restart now uses os.getpid() to reliably target the current process, and sys.executable (quoted) to restart on seedsigner-os.
• Added a safety stop-path: if ResetScreen exits via exception, the reset thread is stopped to avoid killing the running process during screenshot/test scenarios.
• Added unit tests validating the exact subprocess command constructed in each environment branch and verifying the “stopped thread” no-op behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/seedsigner/views/view.py	Updates RestartView reset-thread behavior to kill by PID and restart using sys.executable, plus stops the thread on abnormal screen exit.
tests/test_flows_view.py	Adds tests that assert the constructed reset commands for seedsigner-os vs desktop and ensure the thread skips the kill when stopped.