feat: add server, workstation, and cloud edition manifests

Define the three flagship editions as plain-text manifests:

- server (bastion): production server - observability stack, containers.
- workstation (forge): curated KDE Plasma + dev toolchains.
- cloud (nimbus): cloud kernel, cloud-init, guest agents.

Each manifest carries metadata (services to enable/mask), a package
list, a hardened kernel cmdline, and a btrfs fstab template.

editions/workstation/metadata.yaml

@@ -0,0 +1,33 @@
+# Edition manifest: Arcline Workstation
+# Codename: forge
+edition: workstation
+codename: forge
+summary: Same hardened base with a lightweight KDE Plasma desktop and pre-configured dev toolchains.
+description: >
+  A hardened daily driver. Lightweight KDE Plasma, privacy-hardened browser
+  profiles, pre-configured Go / Rust / Python / Node toolchains, and the same
+  zero-telemetry, default-deny firewall as the server edition.
+
+image:
+  type: iso
+  boot: bios+efi
+  filesystem: btrfs
+  compression: zstd:3
+
+packages:
+  extra_repos: []
+
+users:
+  - arcline
+
+services:
+  enabled:
+    - systemd-networkd
+    - systemd-resolved
+    - nftables
+    - apparmor
+    - sddm
+    - arcline-snapshot.timer
+  masked:
+    - apt-daily.timer
+    - apt-daily-upgrade.timer