feat(waybar): open a calendar (calcurse) on the clock click

Item 42, de-scoped by Bernardo to app-only — no account sync (the user
configures that themselves locally). Clicking the Waybar date/clock now
runs nomarchy-calendar → calcurse in a floating, centered ghostty window
tagged --class=com.nomarchy.calendar (+ --gtk-single-instance=false for a
fresh standalone window), matched by a float+size+center windowrule. The
launcher self-gates on calcurse. Dropped the clock's format-alt date
toggle (conflicts with on-click) and moved the long date into the tooltip.
Parity: on-click added to all four whole-swap jsoncs.

Ships calcurse + pwvucontrol uncommented in the downstream template
(opt-out). Enforces ghostty always installed (ghostty.nix: enable = true
unconditional; nomarchy.ghostty.enable now gates only the theming/config)
so the --class launcher can rely on it.

Verified: V0 green; four jsoncs valid JSON; V1 HM built — launcher ships,
generated clock renders on-click=nomarchy-calendar (format-alt gone, date
in tooltip), hyprland has the 3 calendar windowrules, ghostty in the HM
profile. Click→float→calcurse month view is V3 (queued). Sync is
deliberately the user's own config, not a distro feature.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

themes/boreal/waybar.jsonc

@@ -39,6 +39,7 @@
   },
   "clock": {
     "format": "{:%H:%M}",
+    "on-click": "nomarchy-calendar",
     "tooltip": true,
     "tooltip-format": "{:%Z (UTC%z)}\n<tt><small>{calendar}</small></tt>"
   },