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/seerr.nix

@@ -1,13 +1,10 @@
 { ... }:
 
-# Seerr (formerly Jellyseerr) — request manager for Jellyfin, talks to
-# Sonarr/Radarr to fulfill requests. Fresh install, no migrated data.
-#
-# configDir stays at the module default; bind-mount AppData onto it instead
-# of overriding configDir, so data lives on the RAID array and survives an
-# OS-disk reinstall (same DynamicUser/StateDirectory issue as prowlarr.nix —
-# see that file for why, and why the mount targets /var/lib/private/seerr
-# rather than the public path).
+# Seerr (formerly Jellyseerr) — request manager for Jellyfin, talking to
+# Sonarr/Radarr; fresh install, no migrated data. configDir stays at the
+# module default, with AppData bind-mounted onto it instead (same
+# DynamicUser/StateDirectory issue as prowlarr.nix — see that file for why,
+# and why the mount targets /var/lib/private/seerr rather than the public path).
 {
   services.seerr.enable = true;