Add modular interactive widgets to the Quickshell bar

Introduces a widgets/ directory of first-party QML modules and a common/
helpers library. Widgets auto-load by name from
default/quickshell/bar/widgets/<name>.qml — no edits to shell.qml needed
for additions beyond the firstPartyWidgets registry.

New widgets (all orientation-aware, top/bottom/left/right):
- media: MPRIS now-playing with scrolling label, cover art popup,
  play/pause/skip controls
- audioPanel: master volume slider, output device picker, per-app mixer
- networkPanel: Wi-Fi scan + connect, current connection details
- bluetoothPanel: paired device list, connect/disconnect, battery
- calendar: month grid popup keyed to today
- notificationCenter: live notification feed, DND toggle, clear all
- brightness: slider popup with scroll-to-adjust
- powerProfile: power-saver/balanced/performance picker (UPower)
- systemStats: inline CPU + RAM sparklines, expanded popup with btop
- weatherFlyout: weather popup with refresh and full report
- workspacesPro: animated focus indicator that slides between workspaces
- powerMenu: lock/suspend/log out/reboot/shutdown popup
- idleInhibitor: coffee-cup toggle wired to omarchy-toggle-idle
- microphone: mic state + mute toggle + scroll volume

Common helpers (default/quickshell/bar/common/):
- WidgetButton: hover/press scale animation, tooltip integration
- PopupCard: orientation-aware anchor + slide-in opacity transition
- Slider: drag/wheel-able linear slider with knob hover bump
- PillButton: rounded action button with icon + label

Bar root gains requestPopout/releasePopout so only one popup is open at
a time across widgets.

Updates bar-defaults.json to ship the new widgets out of the box while
keeping the legacy modules available.

default/quickshell/bar/widgets/weatherFlyout.qml

@@ -0,0 +1,142 @@
+import QtQuick
+import Quickshell
+import Quickshell.Io
+import "../common" as Common
+
+Item {
+  id: root
+
+  property QtObject bar: null
+  property string moduleName: "weatherFlyout"
+  property var settings: ({})
+
+  property bool popupOpen: false
+
+  function closePopout() { popupOpen = false }
+  property var forecast: ({})
+  property string fullReport: ""
+
+  readonly property string label: bar ? bar.weatherText : ""
+  readonly property string klass: bar ? bar.weatherClass : ""
+
+  visible: label !== ""
+  implicitWidth: button.implicitWidth
+  implicitHeight: button.implicitHeight
+
+  function refresh() {
+    if (!forecastProc.running) forecastProc.running = true
+  }
+
+  function parseForecast(text) {
+    var lines = String(text || "").split("\n")
+    var data = { location: "", current: "", hourly: [], daily: [] }
+    var section = ""
+
+    for (var i = 0; i < lines.length; i++) {
+      var line = lines[i]
+      if (i === 0 && line.indexOf("Weather report:") === 0) {
+        data.location = line.replace("Weather report:", "").trim()
+      } else if (line.match(/^[├└]\s/)) {
+        section = "daily"
+      }
+    }
+    return data
+  }
+
+  Process {
+    id: forecastProc
+    command: ["bash", "-lc", "curl -fsS --max-time 5 'wttr.in/?T0&format=%l:+%C+%t+%f+wind+%w+%h+humidity' 2>/dev/null"]
+    stdout: StdioCollector {
+      waitForEnd: true
+      onStreamFinished: root.fullReport = String(text || "").trim()
+    }
+  }
+
+  Common.WidgetButton {
+    id: button
+    anchors.fill: parent
+    bar: root.bar
+    text: root.label
+    active: root.klass === "active"
+    horizontalMargin: 7.5
+    tooltipText: root.fullReport || "Weather"
+
+    onPressed: function(b) {
+      if (b === Qt.RightButton) root.bar.run("omarchy-notification-send \"$(omarchy-weather-status)\"")
+      else {
+        root.popupOpen = !root.popupOpen
+        if (root.popupOpen) root.refresh()
+      }
+    }
+  }
+
+  Common.PopupCard {
+    anchorItem: button
+    owner: root
+    bar: root.bar
+    open: root.popupOpen
+    contentWidth: 320
+    contentHeight: column.implicitHeight + 28
+
+    Column {
+      id: column
+      anchors.fill: parent
+      spacing: 10
+
+      Row {
+        spacing: 12
+        width: parent.width
+
+        Text {
+          text: root.label || "—"
+          color: root.bar.foreground
+          font.family: root.bar.fontFamily
+          font.pixelSize: 28
+          anchors.verticalCenter: parent.verticalCenter
+        }
+
+        Column {
+          anchors.verticalCenter: parent.verticalCenter
+          spacing: 2
+
+          Text {
+            text: "Weather"
+            color: root.bar.foreground
+            font.family: root.bar.fontFamily
+            font.pixelSize: 12
+            font.bold: true
+          }
+
+          Text {
+            text: root.fullReport || "Fetching forecast…"
+            color: Qt.darker(root.bar.foreground, 1.2)
+            font.family: root.bar.fontFamily
+            font.pixelSize: 10
+            wrapMode: Text.WordWrap
+            width: 220
+          }
+        }
+      }
+
+      Common.PillButton {
+        width: parent.width
+        iconText: ""
+        text: "Refresh"
+        foreground: root.bar.foreground
+        horizontalPadding: 10
+        verticalPadding: 6
+        onClicked: root.refresh()
+      }
+
+      Common.PillButton {
+        width: parent.width
+        iconText: ""
+        text: "Open wttr.in"
+        foreground: root.bar.foreground
+        horizontalPadding: 10
+        verticalPadding: 6
+        onClicked: { root.bar.run("xdg-open https://wttr.in"); root.popupOpen = false }
+      }
+    }
+  }
+}