Stop tracking fiction, and stop carrying 80 MiB of wallpaper per clone

Three things were in history that should not have been, all invisible to the
tool that deploys them:

- `home/dank/.omp/dotfiles/**` — 3 files re-hosting `niri/cfg/autostart.kdl`,
  `niri/cfg/keybinds.kdl` and `systemd-user/…/swayidle-lock.service` under a
  prefix `scripts/deploy.sh` never reads (it walks `dotfiles/<pkg>/`). The live
  package is deployed and symlinked, so the copy asserted nothing; it only
  misled. Moved to `.AGENTTRASH/20261020-tracked-debt/`.
- `.pre-pull-backup/**` — 2 managed-skill files, a local backup in history,
  which `.gitignore` itself declares must stay on disk only. Same destination.
- `dotfiles/noctalia/.local/share/noctalia/wallpapers/` — 23 images, 80.4 MiB.
  Untracked, files left in place: `~/.local/share/noctalia/wallpapers` symlinks
  into this directory and the theme reads it, so deleting them would have gone
  black. Every filename carries its wallhaven ID, so a fresh box restores the
  set with one `curl` per file plus `deploy.sh`; losing the set is an acceptable
  outcome, 80 MiB per clone forever is not.

New page `omp-docs/tools/dotfiles-deploy.md` owns the deploy contract (the
`--check`/sync/`--adopt` modes, `zz-$(hostname)` override semantics, the dconf
and systemd-user special cases) because nothing documented it, plus two laws:
media the pipeline consumes is content not config, and `systemctl --user
enable` snapshots an absolute path — so enabling from a worktree means the
seven-day reap silently kills the unit while `is-enabled` keeps answering
`enabled`. That second law is not theoretical:
`default.target.wants/blankpad-desk-autoswitch.service` pointed into the reaped
`wt/de-redesign-20261009` and desk auto-switching had been off since. It is
relinked to `dotfiles/zz-blankpad/` and left inactive rather than started mid-
session; starting it applies a desk profile.

Refs #40

omp-docs/tools/index.md

@@ -9,6 +9,7 @@ Configuration guides and reference material for installed software. Each tool ha
 * [applications](applications.md) — Default userspace applications on CachyOS with Niri — browsers, editor, terminal, file manager, audio, screenshots, gaming.
 * [cachyos](cachyos.md) — Arch-based rolling release with performance-optimized kernels, repositories, and gaming stack. Running on the workstation.
 * [comfyui](comfyui/index.md) — Node-based AI image generation engine on dankclaw. FLUX.2 klein 4B, CPU backend, systemd managed.
+* [dotfiles-deploy](dotfiles-deploy.md) — How `dotfiles/` packages become live config: `deploy.sh` modes, host override packages, and why theme media and worktree-enabled units are traps.
 * [ghostty](ghostty/index.md) — GPU-accelerated terminal emulator with extensive configuration, keybindings, and shaders.
 * [gitea](gitea/index.md) — Private Git hosting on dankclaw. Quadlet-managed containers: Gitea, PostgreSQL, Caddy.
 * [handy](handy.md) — Offline speech-to-text transcription with WebKitGTK backend and Tauri v2 UI.