v0.7.0

Fedora support

• Phoenix now installs on Fedora and its derivatives (Nobara, Ultramarine,
  Bazzite) on x86_64 / aarch64 — detect_os grows a third target and the
  installer dispatches to a dnf path (DNF_PACKAGES + the shared Linux
  extras). phoenix-term doctor and preflight gained Fedora arms too.
• Ghostty on Fedora installs from the scottames/ghostty COPR, with a
  manual-install fallback printed if it can't (Phoenix still runs in any
  truecolor terminal).
• RHEL/Rocky/Alma stay unsupported — they advertise ID_LIKE=fedora but
  ship a different package set, so they're rejected explicitly rather than
  installed into a broken state.

tldr fixed on Debian 13 (and hardened everywhere)

• Debian 13 (trixie) removed the tldr package, so it silently went missing.
  Phoenix now installs tealdeer (whose binary is tldr) via a dedicated
  installer: native package on Debian 11/12/13, Ubuntu, and Fedora, with an
  upstream static-binary fallback for any spin that packages neither. Existing
  Debian/Ubuntu users keep tldr exactly as before.