ci: add V1 build tier to automated lock bumps

agent/BACKLOG.md

@@ -316,36 +316,6 @@ implement. Bernardo moves accepted items into a tier.*
   pairs with a hardware-queue session. Recommend (a) now, (b)
   investigated when the T14s is next available.
 
-- **[stability] Interim build-tier gate for automated lock bumps**
-  (surfaced by the 2026-07-08 stability survey, iteration #71). Today
-  `.gitea/workflows/bump.yml` pushes a lock bump to `main` on the
-  **eval tier only** (`nix flake check --no-build`), and Nomarchy ships
-  **no binary cache** — so users pull `main` and *compile* whatever
-  landed. A bump that evaluates but fails to *build* (a dropped patch, an
-  IFD/Stylix break, an upstream package that no longer compiles) reaches
-  users as a broken `home-update`/`sys-rebuild`. Item 20 (VM suite in CI)
-  is the real fix but is `[human]`-blocked on a KVM runner. Cheap interim
-  that needs **no KVM**: have the bump gate additionally *build*
-  `homeConfigurations.nomarchy.activationPackage` and
-  `nixosConfigurations.nomarchy.config.system.build.toplevel` before the
-  push (V1 tier — catches build-time breakage eval misses). Cost/open
-  question: the docker `act_runner` compiles Nomarchy's own derivations
-  from source (cache.nixos.org still serves upstream), so a full toplevel
-  build could be slow/heavy — measure once; if too heavy, gate on the HM
-  activation package alone (the surface most bumps touch). Does not
-  replace item 20; it raises the floor until item 20 lands.
-
-
-
-
-- **[usefulness] External monitor brightness control (ddcutil)**: Laptops
-  can dim their internal screens via `brightnessctl` and the OSD keys, but
-  external monitors connected to a dock are stuck at blinding brightness
-  unless the user reaches for physical buttons. Integrating `ddcutil` (which
-  controls external monitors via DDC/CI over HDMI/DP) into a Waybar slider
-  or a new rofi menu row would give Nomarchy a true "docked workstation"
-  polish. Cost: moderate — requires `hardware.i2c.enable = true`, adding
-  `ddcutil` to udev/groups, and building a UI path to control it.