init layout, notifications, tabs & more

Signed-off-by: Hadi <112569860+anotherhadi@users.noreply.github.com>

notification/README.md

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+# notification
+
+Toast-style notifications, triggered from anywhere in a bubbletea program via an exported
+`tea.Msg` (`ShowMsg`/`Show`) rather than a direct reference to the `Model` that ends up rendering
+them - standard Elm architecture, no IPC between processes.
+
+It composites over an already-rendered string, so it has no dependency on
+`github.com/anotherhadi/ilovetui/layout`: the same `Model` works whether the host uses `layout`
+for its main content or not.
+
+## Quick start
+
+```go
+import (
+	"github.com/anotherhadi/ilovetui/notification"
+)
+
+type model struct {
+	notif         notification.Model
+	width, height int
+}
+
+func newModel() model {
+	return model{notif: notification.New()}
+}
+
+func (m model) Init() tea.Cmd { return m.notif.Init() }
+
+func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	switch msg := msg.(type) {
+	case tea.KeyPressMsg:
+		if msg.String() == "s" {
+			return m, notification.Show("Saved", "Config written to disk", notification.Success)
+		}
+	}
+
+	var cmd tea.Cmd
+	m.notif, cmd = m.notif.Update(msg)
+	return m, cmd
+}
+
+func (m model) View() tea.View {
+	background := renderYourUI(m.width, m.height)
+	view := tea.NewView(m.notif.Render(background))
+	view.AltScreen = true
+	return view
+}
+```
+
+Any component in the same bubbletea program can trigger a toast via `notification.Show`, without
+holding a reference to the `notification.Model` that will actually render it - that `Model` just
+needs to see every `tea.Msg` the program produces (i.e. get its `Update` called from the top-level
+`Update`), same as any other child model.
+
+## Showing and dismissing
+
+```go
+return m, notification.Show("Saved", "Config written to disk", notification.Success)
+
+return m, notification.Show("Sticky", "Stays until dismissed",
+	notification.Info, notification.WithID("sticky-demo"), notification.WithDuration(0))
+return m, notification.Dismiss("sticky-demo")
+```
+
+Four kinds: `Info`, `Success`, `Warning`, `Error`, each with its own color preset (see Styling
+below). By default a toast auto-dismisses after `notification.DefaultDuration` (3s);
+`WithDuration(0)` makes it sticky - it stays until `Dismiss(id)` removes it, so a sticky toast
+needs `WithID` to be dismissable later (an auto-generated id is never returned to the caller).
+Showing again with the same id replaces the toast in place, resetting its position and timer,
+instead of stacking a duplicate.
+
+## Position and stacking
+
+```go
+n := notification.New(notification.WithPosition(notification.TopRight))
+```
+
+Six anchors: `Top`, `TopLeft`, `TopRight`, `Bottom`, `BottomLeft`, `BottomRight` - toasts always
+hug an edge or corner, never the middle of the screen. Multiple toasts stack along the anchored
+edge, newest closest to it; a stack that overflows the background's height clips the oldest
+toasts first, so the newest ones stay visible.
+
+## Styling
+
+```go
+n := notification.New(notification.WithMaxWidth(40), notification.WithStyles(myStyles))
+
+return m, notification.Show("Title", "Message", notification.Success,
+	notification.WithToastStyle(oneOffStyle))
+```
+
+`WithMaxWidth` caps how wide a toast box can grow before its message wraps; a toast narrower than
+the cap shrinks to fit its content instead of padding out to it. A toast can also never overflow
+past the edge of whatever background it's rendered on, regardless of this cap. `WithStyles` sets
+the default per-`Kind` look for every toast shown by this `Model`; `WithToastStyle` (a `Show`
+option) overrides it for one toast alone. `DefaultStyles()` builds from `style.S`: `Info` uses
+`Primary` (no dedicated "info" color in the theme), `Success`/`Warning`/`Error` use their matching
+`style.S` alias.
+
+## Examples
+
+- `examples/notification` - all four kinds, a sticky toast with manual dismiss, cycling through
+  all six positions.