Tether 2.0.1 (security fix)

Security fix; please update, including the helper (the app asks you to).

• Fixed a local privilege escalation. 2.0.0 left /Library/Application Support/Tether writable by
  the admin group and the root helper wrote its files through predictable temporary names, so a
  process running as an administrator could, without the password, make the helper overwrite or
  change the mode of other files as root. The folder is now root's alone, control.json is rewritten
  in place with links and hard links refused, the helper's own files go through mkstemp and
  rename, oversized files aren't read, and both the installer and the helper's start take the
  folder back and remove anything unexpected in it.
• The watchdog runs with a fixed PATH, and a path read from control.json can't add lines to the
  helper log.
• CI: actions/checkout@v7 pinned to its commit, read-only token, Dependabot for actions.

Tether 2.0.0

Superseded by 2.0.1, a security fix. Please install 2.0.1 instead, including its helper.

First public release.

• Clamshell mode follows power: on while connected, off on battery, and a Mac already closed is put
  to sleep the moment it's unplugged. Its switch turns it off until power is connected again.
• No lock: the screen under the lid is dimmed instead of sleeping the display. Optionally lock
  when the lid closes instead.
• Battery hold with safety limits enforced by the helper (battery temperature by lid state,
  thermal pressure, battery floor, time), adjustable only toward stricter values.
• Heat guard: Low Power Mode for a closed Mac running hot on power, and sleep if it keeps
  overheating with no display attached (a bag on a power bank counts as power).
• Low Power Mode only where you allow it (during battery holds; when hot on power, from "serious",
  from "fair" or never), and your own change to it is never undone.
• A watchdog LaunchDaemon that turns sleep back on if the helper ever stops while sleep is off on
  battery.
• A Mac put to sleep on power stays asleep through Power Nap's dark wakes; a charger that can't
  keep up can no longer run the battery flat with the lid closed; a battery hold can't start at or
  below the floor; the app relaunches after a crash.
• Data-based settings: time-weighted battery temperatures, battery use during holds, and
  recommended limits from them; "Adjust to this Mac" applies them by itself as measurements come
  in, never looser than the defaults.
• Sleep log: duration, charge per hour, sleep and wake causes, dark wakes; alerts on high drain.
• Screen off without locking after a few idle minutes.
• tether command with status --json, hold, sleep, run -- <command> and diagnose.
• tether:// URLs for the Shortcuts app.
• Apps keeping the Mac awake, live in Settings and tether status.
• Troubleshooting: detailed logging and a Markdown report with masked names, from Settings or
  tether diagnose --record.
• Control Center style panel (full and compact) with a clamshell switch and a countdown to the
  second; a status item with a ring that empties during a battery hold.
• Icon Composer app icon (Liquid Glass, dark, clear and tinted), sidebar settings, English and
  Korean with a choice in Settings.
• tether doctor and a checks list in Settings › System and at the top of the report; "+30m"
  for a running battery hold (tether hold +30m), still capped at 4 hours from its start.
• In-place help: an ⓘ next to each setting that needs explaining (what it does, the words it
  uses), Help › Tether Help opening the README, and a glossary in the README.
• First-run welcome, update check against GitHub releases, full uninstall.
• A quiet panel: controls that can't act right now are hidden rather than greyed out, and there
  are no lid-open or toggle notifications (the last lid session is in the panel and History).
• Desktop Macs are left alone.