fix: repair skill frontmatter and cap commit message length

.agents/skills/nix-config-debug/SKILL.md

@@ -1,9 +1,9 @@
 ---
 name: nix-config-debug
-description:
+description: >-
   Use when something here is broken or stops working: an eval or build error, a failed activation, a
-  dead or restarting unit, a mihomo or DNS outage, an unreachable host or MicroVM guest, or a failing
-  CI action.
+  dead or restarting unit, a mihomo or DNS outage, an unreachable host or MicroVM guest, or a
+  failing CI action.
 ---
 
 # Debugging this repository

.agents/skills/nix-config-desktop/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: nix-config-desktop
-description:
+description: >-
   Use when changing what the desktop shows or runs: Niri/Noctalia config, a window that is the wrong
   size, garbled, or missing after a reboot, autostart, fcitx5 or vinput input, theming and fonts,
   interface names a widget reads, or `$HOME` state that must survive a tmpfs root.

.agents/skills/nix-config-update/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: nix-config-update
-description:
+description: >-
   Use when a version changes here: upgrading or updating a package or nixpkgs, bumping or pinning a
   flake input (a tag or commit, not a branch), or deploying the result to hosts, VMs, and MicroVM
   guests.