feat(menu): hyprpicker color picker — Tools › row + SUPER+CTRL+P (item 13 done)

The last niceties slice: pick a pixel's color into the clipboard.
hyprpicker joins grim/slurp in systemPackages; a new nomarchy-menu
`colorpicker` mode captures its output, wl-copies it, and toasts the
hex (Esc = silent cancel). Tools › row self-gates on hyprpicker being
present; SUPER+CTRL+P added in keybinds.nix, so the Hyprland bind and
the SUPER+? cheatsheet row come from the one source. Item 13 complete
and deleted from BACKLOG.

Verified: V0 (flake check); V1 — template-home and template-system
build; rendered nomarchy-menu passes bash -n and contains the mode +
gated row; cheatsheet has the SUPER+CTRL+P row; hyprland.conf has the
bind; the system toplevel ships sw/bin/hyprpicker. Remains: V3 — real
loupe → click → wl-paste round-trip in a session (HARDWARE-QUEUE).

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

agent/BACKLOG.md

@@ -26,13 +26,6 @@ next, in what order*.
 
 ## NEXT
 
-### 13. Small niceties batch (one slice per iteration)
-Each is a small, self-contained polish item in the existing patterns
-(shipped: idle-inhibit/caffeine 2026-07-04; low-battery notifications
-2026-07-05 — sysfs watcher + checks.battery-notify):
-- **Color picker:** `hyprpicker` → clipboard as a Tools › entry +
-  `SUPER+CTRL` bind; pairs naturally with theme work.
-
 ### 14. Automated upstream lock bumps (maintainer CI, slices b+c) `[big]`
 ROADMAP § Automated upstream lock bumps — the scheduled half (the
 checks-on-push workflow shipped; see item 20 for the runner status):