capture: close dialog on Archive; rich per-URL and batch toast notifications (#22)

* http: realistic UA; fall back to WebPage on probe failure

Replace bare 'archivr/0.1' user agent with a full Chrome 131 UA string
(archivr/0.1 token retained at the end) in both probe_url_kind and download.

More importantly, stop hard-failing when probe_url_kind returns an error.
Sites behind Cloudflare's managed JS challenge (e.g. Medium) return 403
before any header tuning can help — a plain HTTP client cannot pass the
challenge. Instead, log a warning and fall back to Source::WebPage so that
the SingleFile/Chromium path gets a chance; a real browser can solve the
challenge transparently.

* capture: close dialog on Archive; rich per-URL and batch toast notifications

UX changes:
- Pressing Archive closes the capture dialog immediately; jobs continue
  polling in the background (component stays mounted).
- Probe failures (e.g. Cloudflare JS challenge, HTTP 403) now fall back to
  Source::WebPage so SingleFile/Chromium can attempt the capture instead of
  hard-failing at the probe stage.

Toast notifications:
- Single URL: green 'Archived' on success, amber 'Archived with warnings'
  (with expandable detail) when uBlock/cookie-ext was skipped, red 'Capture
  failed' with expandable error text on failure. Per-item warning/error toasts
  include the locator so the user knows which URL was affected.
- Multi-URL batch: per-item failure and warning toasts still fire with
  locators; per-item success toasts are suppressed. Once all jobs settle a
  single summary toast fires: 'N archived', 'N archived (M with warnings)',
  'N archived (M with warnings), F failed', or 'N failed'. The summary Detail
  section lists the exact URLs that failed or warned, so the user retains that
  information after per-item toasts auto-dismiss.
- Batch summary color: green = all clean; amber = any warnings or failures
  present; red = all failed.
- handleIgnoreUblock now only removes per-item warning toasts (those with a
  locator) and persists the ignore flag; batch summary warnings (locator=null)
  are not swept.

ToastStack improvements:
- All three branches (success/warning/error) support a toast.headline field
  so batch summaries can set their own copy.
- Warning branch: Details button conditional on toast.text; Ignore button
  conditional on toast.locator (uBlock-specific, not shown on batch summaries).
- Locator display uses hostname/…/last-segment for URLs (preserves domain for
  context, tail for identity) and tail-truncation for shorthands; full locator
  in title attribute for hover.
- Icon colors: green for success (✓), amber for warning (⚠), red for error (✕).

frontend/src/components/ToastStack.jsx

@@ -13,9 +13,27 @@ export default function ToastStack({ toasts, onDismiss, onIgnoreUblock }) {
   )
 }
 
+// For URLs: show hostname/…/tail (drops protocol + middle path, keeps domain + identifier).
+// For shorthands (yt:, x:, etc.): keep the tail since it's the whole identifier.
+// CSS text-overflow:ellipsis on .toast-locator handles any remaining overflow.
+function shortLocator(locator) {
+  if (!locator) return null
+  if (locator.length <= 52) return locator
+  try {
+    const { hostname, pathname, search } = new URL(locator)
+    const segments = pathname.split('/').filter(Boolean)
+    const tail = (segments[segments.length - 1] ?? '') + search
+    const candidate = tail ? `${hostname}/\u2026/${tail}` : hostname
+    return candidate.length <= 56 ? candidate : candidate.slice(0, 53) + '\u2026'
+  } catch {
+    return '\u2026' + locator.slice(-51)
+  }
+}
+
 function Toast({ toast, onDismiss, onIgnoreUblock }) {
   const [expanded, setExpanded] = useState(false)
   const isWarning = toast.type === 'warning'
+  const isSuccess = toast.type === 'success'
 
   // Auto-dismiss after TTL; paused while detail is expanded
   useEffect(() => {
@@ -24,9 +42,24 @@ function Toast({ toast, onDismiss, onIgnoreUblock }) {
     return () => clearTimeout(timer)
   }, [expanded, toast.id, onDismiss])
 
-  const short = toast.locator
-    ? (toast.locator.length > 48 ? toast.locator.slice(0, 45) + '\u2026' : toast.locator)
-    : null
+  const short = shortLocator(toast.locator)
+
+  if (isSuccess) {
+    return (
+      <div className="toast toast--success" role="alert" aria-atomic="true">
+        <div className="toast-top">
+          <span className="toast-icon" aria-hidden="true">✓</span>
+          <div className="toast-body">
+            <span className="toast-headline">{toast.headline || 'Archived'}</span>
+            {short && <span className="toast-locator" title={toast.locator}>{short}</span>}
+          </div>
+          <div className="toast-btns">
+            <button type="button" className="toast-dismiss" onClick={() => onDismiss(toast.id)} aria-label="Dismiss">×</button>
+          </div>
+        </div>
+      </div>
+    )
+  }
 
   if (isWarning) {
     return (
@@ -34,25 +67,29 @@ function Toast({ toast, onDismiss, onIgnoreUblock }) {
         <div className="toast-top">
           <span className="toast-icon" aria-hidden="true">⚠</span>
           <div className="toast-body">
-            <span className="toast-headline">Ad-blocking unavailable</span>
-            {short && <span className="toast-locator">{short}</span>}
+            <span className="toast-headline">{toast.headline || 'Archived with warnings'}</span>
+            {short && <span className="toast-locator" title={toast.locator}>{short}</span>}
           </div>
           <div className="toast-btns">
-            <button
-              type="button"
-              className="toast-view-btn"
-              onClick={() => setExpanded(v => !v)}
-              aria-expanded={expanded}
-            >
-              {expanded ? 'Hide' : 'Details'}
-            </button>
-            <button
-              type="button"
-              className="toast-view-btn toast-ignore-btn"
-              onClick={() => { onIgnoreUblock?.(); onDismiss(toast.id) }}
-            >
-              Ignore
-            </button>
+            {toast.text && (
+              <button
+                type="button"
+                className="toast-view-btn"
+                onClick={() => setExpanded(v => !v)}
+                aria-expanded={expanded}
+              >
+                {expanded ? 'Hide' : 'Details'}
+              </button>
+            )}
+            {toast.locator && (
+              <button
+                type="button"
+                className="toast-view-btn toast-ignore-btn"
+                onClick={() => { onIgnoreUblock?.(); onDismiss(toast.id) }}
+              >
+                Ignore
+              </button>
+            )}
             <button
               type="button"
               className="toast-dismiss"
@@ -65,7 +102,7 @@ function Toast({ toast, onDismiss, onIgnoreUblock }) {
         </div>
         {expanded && (
           <p className="toast-warning-detail">
-            {toast.text || 'ARCHIVR_UBLOCK=true but ARCHIVR_UBLOCK_EXT is not set or the path is invalid. The page was captured without ad-blocking. Set ARCHIVR_UBLOCK_EXT to the unpacked uBlock Origin Lite extension directory to enable ad-blocking, or set ARCHIVR_UBLOCK=false to silence this warning.'}
+            {toast.text || 'The page was captured but one or more browser extensions were unavailable (ad-blocking or cookie-consent). Check ARCHIVR_UBLOCK_EXT and ARCHIVR_COOKIE_EXT in your server config.'}
           </p>
         )}
       </div>
@@ -77,8 +114,8 @@ function Toast({ toast, onDismiss, onIgnoreUblock }) {
       <div className="toast-top">
         <span className="toast-icon" aria-hidden="true">✕</span>
         <div className="toast-body">
-          <span className="toast-headline">Capture failed</span>
-          {short && <span className="toast-locator">{short}</span>}
+          <span className="toast-headline">{toast.headline || 'Capture failed'}</span>
+          {short && <span className="toast-locator" title={toast.locator}>{short}</span>}
         </div>
         <div className="toast-btns">
           {toast.text && (