feat(errors): classify the install 'no store entry' failure

Even with the honest install badge the hub error stays reachable
(stale store snapshot, race with a store refresh, older hub). The
friendly-error mapper now gives it its own headline plus a hint
naming the three acquisition paths — local module install, adding
the providing store, configuring the MCP/n8n integration — in EN
and DE, with the verbatim hub message kept copyable. Matcher unit
tests EN+DE guard the classification.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/data/friendly_error.dart

@@ -204,6 +204,20 @@ FriendlyError? _matchHubPattern(String detail, AppLocalizations l) {
       hint: l.errMcpUnreachableHint,
     );
   }
+  // Install target unresolvable — the hub's install resolver found
+  // no store entry with that exact name ("no store entry for 'X' —
+  // hint"). Distinct from capability-not-installed below: the store
+  // cannot deliver it at all, so the recovery is one of the three
+  // acquisition paths, not the Fix button. Reachable despite the
+  // honest badge (stale store snapshot, race with a store refresh,
+  // older hub).
+  if (detail.contains('no store entry for')) {
+    return FriendlyError(
+      headline: l.errNoStoreEntry,
+      detail: detail,
+      hint: l.errNoStoreEntryHint,
+    );
+  }
   // Capability not in registry — hub returns NotFound with this
   // shape from the flow engine.
   if (detail.toLowerCase().contains('no capability provider') ||