chore(theme): use upstream tmux template

[CollieIsCute]

Summary

• remove the temporary Linux tmux user-template downloader
• enable the published Noctalia community tmux template
• make macOS Matugen follow the official upstream main tmux template and reload hook, refreshed every 24 hours
• refresh stale Fish and macOS wallpaper documentation

Ownership

• Linux: Noctalia community catalog owns the tmux template and generated theme
• macOS: Matugen fetches the current upstream main template inputs through chezmoi
• chezmoi continues to manage only generator configuration and the stable tmux source line

The macOS externals intentionally omit fixed checksums: a checksum would make the floating main URLs fail as soon as upstream changes. refreshPeriod = "24h" keeps the cache current; chezmoi apply -R forces an immediate refresh. This means the upstream apply.sh hook is trusted when it changes.

Verification

• noctalia config validate home/dot_config/noctalia
• noctalia theme --list-templates -c home/dot_config/noctalia/config.toml
• rendered the official tmux template with Noctalia in faithful/light mode and matched the current generated theme byte-for-byte
• downloaded both current upstream main files; they still match the former pinned SHA256 values
• bash -n on the current upstream apply.sh
• parsed rendered Darwin and Windows Matugen/external TOML
• ran the upstream apply hook twice against an isolated tmux 3.7c server; the config stayed idempotent and the generated status colors reloaded live
• git diff --check

Upstream: noctalia-dev/community-templates#101