fix: address Copilot review on release/3.3.2

Non-ASCII glyphs (regression of the #681 class of Windows UnicodeEncodeError):
- mempalace/cli.py: "✗" → "ERROR:", "⚠" → "WARNING:", em dash → "-"
- mempalace/sweeper.py: "⚠" → "WARNING:"

Backend arg validation:
- mempalace/backends/chroma.py: `_normalize_get_collection_args` now
  raises TypeError on unexpected trailing positional args instead of
  silently dropping them — surfaces call-site bugs early.

Docs site:
- website/.vitepress/config.mts: gate Google Analytics scripts behind
  MEMPALACE_DOCS_GA_ID env var (default off). Self-hosters no longer
  get GA injected unconditionally.

Landing page SPA hygiene:
- website/.vitepress/theme/landing/useLandingEffects.js: collect all
  IntersectionObserver disconnects and removeEventListener thunks in a
  shared `cleanups` registry; drain it in `onBeforeUnmount` so observers
  and form/replay listeners don't leak across SPA navigations.

website/.vitepress/config.mts

@@ -11,6 +11,7 @@ function normalizeBase(base?: string): string {
 
 const docsBase = normalizeBase(process.env.DOCS_BASE || '/')
 const editBranch = process.env.DOCS_EDIT_BRANCH || 'main'
+const gaId = process.env.MEMPALACE_DOCS_GA_ID
 
 export default withMermaid(
   defineConfig({
@@ -26,8 +27,10 @@ export default withMermaid(
       ['meta', { property: 'og:title', content: 'MemPalace — AI Memory System' }],
       ['meta', { property: 'og:description', content: '96.6% LongMemEval recall. Zero API calls. Local, free, open source.' }],
       ['meta', { property: 'og:image', content: `${docsBase}mempalace_logo.png` }],
-      ['script', { async: '', src: 'https://www.googletagmanager.com/gtag/js?id=G-PPQE4Z7P1K' }],
-      ['script', {}, `window.dataLayer = window.dataLayer || [];\nfunction gtag(){dataLayer.push(arguments);}\ngtag('js', new Date());\ngtag('config', 'G-PPQE4Z7P1K');`],
+      ...(gaId ? [
+        ['script', { async: '', src: `https://www.googletagmanager.com/gtag/js?id=${gaId}` }],
+        ['script', {}, `window.dataLayer = window.dataLayer || [];\nfunction gtag(){dataLayer.push(arguments);}\ngtag('js', new Date());\ngtag('config', '${gaId}');`],
+      ] as const : []),
     ],
 
     themeConfig: {