docs: condense comments across the repo

Comments had drifted into multi-paragraph narrative (git commit
lineage, debugging stories, restated code) in several hot spots
(scripts/deploy, hermes-agent.nix, flake.nix, gitea.nix, headscale.nix).
Trim every comment to its load-bearing "why" — gotchas, safety
warnings, and non-obvious rationale survive verbatim in substance,
just tightened to 1-2 sentences; historical narrative and anything
already covered in CLAUDE.md is cut. No code/logic changed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UJqEmY1y3AYX3JoX4Y6b21

services/media/audiobookshelf.nix

@@ -1,11 +1,9 @@
 { ... }:
 
-# Audiobookshelf audiobook/podcast server.
-# Listens on all interfaces: :8000 stays closed on the LAN (no openFirewall),
-# but reachable over the trusted tailscale0 interface and via localhost (caddy).
-# Library/media paths are set in the web UI — point them at /mnt/data/...
-# Runs as user `audiobookshelf`; added to `users` so it can read group-owned
-# library dirs on the RAID.
+# Audiobookshelf audiobook/podcast server, listening on all interfaces but
+# reachable only via tailscale0 or local caddy (no openFirewall) — library
+# paths are set in the web UI, pointed at /mnt/data/... In the "users" group
+# so it can read the RAID's group-owned library dirs.
 {
   services.audiobookshelf = {
     enable = true;