fix(renderer): eagerly erase the previous frame on resize in inline mode

[TaraTheStar]

After tea.Println, subsequent terminal resizes can leave the previous live region stranded above the new one and accumulate copies of stale frames in scrollback on each resize event.

insertAbove ends with s.scr.SetPosition(0, 0) to declare the live region's new anchor. resize then only sets ultraviolet's deferred clear flag; the physical erase is deferred to the next Render, which takes the clearUpdate path and emits move(newbuf, 0, 0) followed by EraseScreenBelow. With s.cur == (0, 0), move() short-circuits to zero bytes (see ultraviolet/terminal_renderer.go:439), so ED-0 fires at whatever the physical cursor's position actually is — not necessarily the renderer's logical anchor — and the old frame above is never erased.

Fix: in cursedRenderer.resize, before flipping the deferred clear, write \r + CUU(s.cur.Y) + ED-0 directly to the writer (matching insertAbove's direct-write pattern), then set s.cur = (-1, -1) so moveCursor's first-move safety (terminal_renderer.go:362-368) emits a defensive \r on the next cursor move. Alt-screen is guarded out — it uses absolute positioning and its own clear contract.

Reproducer:

package main

import (
    "fmt"
    "strings"
    tea "charm.land/bubbletea/v2"
)

type m struct{ w, h, n int }

func (m m) Init() tea.Cmd { return nil }
func (m m) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
    switch msg := msg.(type) {
    case tea.WindowSizeMsg:
            m.w, m.h = msg.Width, msg.Height
    case tea.KeyPressMsg:
            switch msg.String() {
            case "q":
                    return m, tea.Quit
            case "p":
                    m.n++
                    return m, tea.Println(fmt.Sprintf("--- println #%d ---", m.n))
            }
    }
    return m, nil
}
func (m m) View() tea.View {
    rows := make([]string, 5)
    for i := range rows { rows[i] = strings.Repeat("=", 30) }
    return tea.NewView(strings.Join(rows, "\n") +
            fmt.Sprintf("\nstatus: %dx%d n=%d\n> _", m.w, m.h, m.n))
}
func main() { tea.NewProgram(m{}).Run() }

Run, press p, then drag-resize the terminal. Pre-fix: old frames stack in scrollback. Post-fix: clean.

A note on reproducibility: I could not reproduce the visual artifact on a Linux PTY with xterm-256color; the wire bytes happen to align there. The mechanism is unambiguous from the source, and the bug has been reported in adjacent contexts (e.g. anthropics/claude-code#49086). Reviewers on iTerm2 / Terminal.app / Windows Terminal
would be best positioned to confirm the visual fix.

• I have read CONTRIBUTING.md.