Inline mode: negative inlineStartRow when the terminal is shorter than the inline height

syncInlineGeometryOnResize sets inlineStartRow = termHeight - inlineHeight without clamping at 0, unlike the startup path (app_inline_startup.go) and resumeTerminal (app_suspend_unix.go), which both use max(..., 0). Shrinking the terminal below the inline height therefore produces a negative start row, and the renderer can emit cursor escapes with negative rows for that frame.

The full-redraw clear path clamps its own clear row at 0 as of the fix for #119, but the underlying geometry is still unclamped: buffer cell changes and cursor placement can still be computed from a negative start row until the terminal grows again. The sync path should clamp the same way the other two paths do, and probably also cap the effective widget height at the terminal height like SetInlineHeight does.