Fix editor E2E placement and disposed texture fallback (#324)

ddiff --git a/apps/client/e2e/editorCheck.ts b/apps/client/e2e/editorCheck.ts
iindex 82fdad2..01f7c01 100644
---- a/apps/client/e2e/editorCheck.ts
++++ b/apps/client/e2e/editorCheck.ts
@@@ -240,9 +240,12 @@ const browser = await chromium.launch({
    args: ['--use-angle=swiftshader', '--enable-webgl', '--disable-gpu-sandbox'],
  })
  const page = await browser.newPage({ viewport: { width: 1400, height: 900 } })
--page.on('pageerror', (e) =>
--  console.log('[pageerror]', String((e as Error).stack ?? e).slice(0, 500)),
--)
++let disposedTextureErrors = 0
++const onPageError = (e: Error): void => {
++  if (e.message.includes('markAllMaterialsAsDirty')) disposedTextureErrors++
++  console.log('[pageerror]', String(e.stack ?? e).slice(0, 500))
++}
++page.on('pageerror', onPageError)
  await page.goto(`http://127.0.0.1:${PORT}/editor`)
  await page.waitForSelector('#save', { timeout: 90_000 })
  await page.waitForFunction(() => Boolean((window as never as { __editor?: unknown }).__editor), {
@@@ -794,9 +797,7 @@ async function withMap(
          localStorage.setItem('ovg_sso', t as string)
          document.cookie = `ovg_sso=${encodeURIComponent(t as string)}; Path=/; SameSite=Lax`
        }, TEST_TOKEN)
--      pg.on('pageerror', (e) =>
--        console.log('[pageerror]', String((e as Error).stack ?? e).slice(0, 500)),
--      )
++      pg.on('pageerror', onPageError)
        await pg.goto(`http://127.0.0.1:${port}/editor`)
        await pg.waitForSelector('#save', { timeout: 90_000 })
        await pg.waitForFunction(
@@@ -1686,14 +1687,40 @@ section('W. Painting imported models')
        zones: [],
      },
      async (pg) => {
--      /** Arm a model and click the viewport to place one, returning its id. */
++      /** Arm a model and click visible terrain, clear of the placement strip. */
        const place = async (modelId: string, x: number, y: number): Promise<string | null> => {
          await probeArgs(pg, ([p, id]) => p.armModel(id as unknown as string), modelId)
--        await pg.mouse.move(x, y)
++        const target = (await probeArgs(
++          pg,
++          ([p, px, py]) => {
++            const canvas = document.getElementById('game')
++            for (const [dx, dy] of [
++              [0, 0],
++              [0, -60],
++              [-80, -60],
++              [80, -60],
++              [0, -120],
++            ]) {
++              const cx = (px as number) + dx
++              const cy = (py as number) + dy
++              if (document.elementFromPoint(cx, cy) === canvas && p.pickIdAt(cx, cy) === 'w-floor')
++                return [cx, cy]
++            }
++            return null
++          },
++          x,
++          y,
++        )) as [number, number] | null
++        if (!target) throw new Error(`no visible terrain near placement point (${x}, ${y})`)
++        const before = (await probeOf(pg, (p) => p.objectCounts())).statics
++        await pg.mouse.move(target[0], target[1])
          await pg.waitForTimeout(200)
          await pg.mouse.down()
          await pg.mouse.up()
          await pg.waitForTimeout(700)
++        const after = (await probeOf(pg, (p) => p.objectCounts())).statics
++        if (after !== before + 1)
++          throw new Error(`model placement created ${after - before} objects`)
          return probeOf(pg, (p) => p.primaryId())
        }
  
@@@ -1952,6 +1979,11 @@ section('V. Performance profile on a large map')
    )
  }
  
++ok(
++  'disposed textures never retry KTX2 fallback',
++  disposedTextureErrors === 0,
++  disposedTextureErrors,
++)
  console.log(
    `\n${'═'.repeat(64)}\n${checks - failures}/${checks} checks passed, ${failures} FAILED\n`,
  )
ddiff --git a/apps/client/src/render/ktx2.ts b/apps/client/src/render/ktx2.ts
iindex 936c207..a2a31ed 100644
---- a/apps/client/src/render/ktx2.ts
++++ b/apps/client/src/render/ktx2.ts
@@@ -73,7 +73,9 @@ export function loadTexture(src: TexSource, scene: Scene): Texture {
    configure()
    let tx: Texture | null = null
    const fallBack = (): void => {
--    if (tx && src.fallback) tx.updateURL(src.fallback)
++    // KTX2 decoding can fail after a material has replaced and disposed this
++    // texture. Babylon clears its scene on dispose; updateURL needs that scene.
++    if (tx?.getScene() === scene && !scene.isDisposed && src.fallback) tx.updateURL(src.fallback)
    }
    tx = new Texture(src.url, scene, false, true, Texture.TRILINEAR_SAMPLINGMODE, null, fallBack)
    return tx