feat(bar): timezone line in the clock tooltip (LATER item)

Hovering the clock now leads with the zone — "{:%Z (UTC%z)}" above the
calendar — on the generated bar and both summer whole-swaps (parity).
Under auto-timezone the existing tz-watch SIGUSR2 reload keeps it
showing the currently detected zone. %Z is the abbreviation (BST), not
the IANA name — strftime has no code for that, and it satisfies the
"(optional)" nicety.

Verified: V0; V1 — the rendered generated config carries the new
tooltip-format and both summer jsonc parse with it. Hover render
queued for hardware.

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

themes/summer-day/waybar.jsonc

@@ -70,7 +70,7 @@
   "clock": {
     "format": " {:%H:%M}",
     "tooltip": true,
-    "tooltip-format": "<tt><small>{calendar}</small></tt>"
+    "tooltip-format": "{:%Z (UTC%z)}\n<tt><small>{calendar}</small></tt>"
   },
 
   "clock#date": {

themes/summer-night/waybar.jsonc

@@ -69,7 +69,7 @@
   "clock": {
     "format": " {:%H:%M}",
     "tooltip": true,
-    "tooltip-format": "<tt><small>{calendar}</small></tt>"
+    "tooltip-format": "{:%Z (UTC%z)}\n<tt><small>{calendar}</small></tt>"
   },
 
   "clock#date": {