fix(tmux): temporarily pin Noctalia template on Linux

[CollieIsCute]

Summary

• Register tmux as a Linux Noctalia user template until feat(tmux): Add tmux template noctalia-dev/community-templates#101 reaches the catalog.
• Lazy-cache the exact PR head template and apply hook; generated colors remain outside chezmoi ownership.
• Keep the workaround to one file and one droppable commit.

Removal

After #101 is published, drop commit 170c340 and add tmux to community_ids.

Verification

• noctalia config validate home/dot_config/noctalia
• Verified pinned file checksums and apply.sh syntax locally.
• Rendered the template with Noctalia and confirmed current, last, activity, and bell styles.