feat(themes): wallpapers split — 94 MB of runtime-only images leave the flake source

The split line is consumption time: palette JSONs, previews and
per-theme overrides are read at Nix eval and stay in-repo (~3 MB);
wallpapers are runtime-only (swww via nomarchy-state-sync, never read
at eval) and move to the pinned nomarchy-wallpapers non-flake input
(git.bemagri.xyz/bernardo/Nomarchy-Wallpapers @ 803b48d, all 24 slugs).

New overlay drv nomarchy-default-themes merges the two: repo themes
copied, <slug>/backgrounds symlinked from the input, build FAILS if any
theme JSON lacks non-empty backgrounds — the drift guard for the
two-repo dance. nomarchy-state-sync's wrapper now points straight at
the merged store path (no in-package copy): the package drops from
~94 MB to 32.6 KiB and the wallpapers source appears exactly once in
any system closure, ISO included — offline promise intact. Downstream
custom wallpapers still win ($NOMARCHY_PATH/themes is checked first),
and an explicit state.json wallpaper path still works.

checks re-pointed at the merged tree (theme-wholeswap,
state-sync-validate, auto-theme); theme-contrast and airplane stay on
./themes (JSON/text only). import-palettes.py + README updated;
ROADMAP § Faster switches marked shipped; LATER now carries only the
pre-built-variants follow-on. Also files #151 (v1 launch plan, [human])
with measured history numbers: the 107 MiB pack is 94 MB wallpaper
blobs; all 848 text commits pack to ~15-20 MiB — recommendation
recorded to filter-repo at the GitHub move, not fresh-start.

Verification: V2 — nix flake check --no-build green; theme-wholeswap,
state-sync-validate, auto-theme VM check, downstream-template-home all
green; wallpapers store path exactly once in the state-sync closure;
`list` works from a scratch state dir. V3 queued: live wallpaper render
+ bg-next + custom-override precedence after next pull (HARDWARE-QUEUE).
Lock gained exactly the one input node. Implementation by a Sonnet
subagent; design and review on Fable.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent/BACKLOG.md

@@ -89,12 +89,43 @@ rofi#2317, and take the fix when a release carries it. If it is still open at
 the next lock bump, that is fine — nothing here rots meanwhile.
 *Last checked 2026-07-17: open, no maintainer response, no linked PR.*
 
+### 151. `[human]` v1 launch plan — devise with Bernardo (includes the GitHub move)
+
+Bernardo, 2026-07-17: before tagging v1, sit down and devise the launch plan.
+Known ingredients, so that session starts concrete:
+- **The repo moves to GitHub.** Everything baking the Gitea URL follows: the
+  downstream template's `inputs.nomarchy.url`, the `nomarchy-wallpapers`
+  input URL (baked 2026-07-17 — sweep it in the same move), README/docs
+  links, and CI (eval CI runs on Gitea act_runner — decide GitHub Actions
+  vs keeping Gitea CI on a mirror).
+- The move is the natural moment for the **history-rewrite decision**, and
+  it is now measured (2026-07-17): the 107 MiB pack is 94.2 MB wallpaper
+  blobs + 9.9 MB preview generations; all 848 commits of *text* pack to
+  ~15–20 MiB. So the history is not long-heavy, it is image-heavy.
+  Recommendation on the table: **filter, don't reset** —
+  `git filter-repo` stripping only `themes/*/backgrounds/` keeps every
+  commit's diffs/blame/`log -S` (load-bearing: it diagnosed #147) at a
+  ~15–20 MiB clone. Cost: all SHAs change, and ROADMAP/journal cite them —
+  mitigate by freezing the Gitea repo as a read-only archive (old SHAs
+  resolve there; stash filter-repo's commit-map in it) + one ROADMAP note.
+  Argue against a full mirror (ships 94 MB of deleted images to every
+  clone forever) and against fresh-start (burns the archaeology to save
+  ~15 MiB).
+- The existing v1 bar (VISION § v1.0): HARDWARE-QUEUE burn-down, install P0
+  re-verify before the `v1` fast-forward, visual ritual. LICENSE shipped
+  (MIT, 2026-07-17).
+- Adjacent calls that may fold in: cachix/public binary cache (#120's
+  prerequisite), the netinstall decision itself, release notes/announce.
+
+`v1` stays human-only throughout — agents prepare evidence and checklists,
+never the tag or branch.
+
 ## LATER
 
-- **Wallpapers artifact split** (ROADMAP § Faster switches — decided,
-  deferred): pinned `Nomarchy-wallpapers` input so a state write stops
-  re-copying 86 MB. Follow-on: pre-built theme variants if switches are
-  still slow after.
+- **Pre-built theme variants** (ROADMAP § Faster switches follow-on): if
+  `home-manager switch` itself is still the theme-switch bottleneck now
+  that the wallpapers split shipped (2026-07-17), pre-build each theme's
+  generation so a switch just activates a cached one. Measure first.
 - **Installer round 2** (ROADMAP § Installer): multi-disk BTRFS RAID,
   impermanence, BIOS/legacy boot.
 - **Boot-from-snapshot**: a systemd-boot equivalent of grub-btrfs.