fix(fips,federation,ui): mesh content browse, removed-node tombstones, modal sizing

FIPS peer content browse over the mesh was failing with "Peer returned
error: 404 Not Found" and never falling back to Tor. `is_peer_allowed_path`
only allowed `/content/<id>` (item fetches) — the catalog endpoint is
exactly `/content` (no trailing slash), so it 404'd over the FIPS peer
listener. A FIPS 404 was also treated as a successful response, so the dial
never retried Tor. Fixes: allow `/content` over the mesh; add
`fips_should_fall_back()` so a FIPS 404/5xx in Auto mode falls back to Tor
(handles version-skew peers reaching a different route). Also correct the
reconnect hint text — the public anchor is TCP/8443, not UDP/8668.

Federation: deleted nodes reappeared because transitive discovery
(`merge` of a peer's advertised trusted peers) re-added any unknown DID.
Add a tombstone store (`removed-nodes.json`): remove_node tombstones the
DID, transitive merge skips tombstoned DIDs, and a remote-triggered
peer-joined is ignored for a removed DID. Explicit local re-add (add_node)
clears the tombstone.

UI: the app credentials modal panel stretched edge-to-edge (height:100%,
max-width:none, items-stretch overlay). Constrain it to a centered card
(max-width 34rem, rounded, dimmed full-screen backdrop) matching the
AppIconGrid / wallet-receive modal.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/archipelago/src/server.rs

@@ -769,6 +769,13 @@ pub fn is_peer_allowed_path(path: &str) -> bool {
             | "/archipelago/mesh-typed"
             | "/dwn"
             | "/transport/inbox"
+            // Content *catalog* — the peer-browse entry point. This is the
+            // exact path `/content` (no trailing slash); the prefix match
+            // below only covers `/content/<id>` item fetches, so without
+            // this the catalog 404s over the mesh and `content.browse-peer`
+            // fails with "Peer returned error: 404 Not Found" (and never
+            // falls back to Tor, since a 404 is a successful HTTP exchange).
+            | "/content"
     )
     // Prefix-matched content endpoints (peer file browse + fetch)
         || path.starts_with("/content/")
@@ -1378,6 +1385,25 @@ mod merge_tests {
         }
     }
 
+    #[test]
+    fn peer_path_filter_allows_content_catalog_and_items() {
+        // Regression: the content *catalog* is exactly "/content" (no trailing
+        // slash). It must be reachable over the peer (FIPS) listener, else
+        // `content.browse-peer` 404s over the mesh. Item fetches are
+        // "/content/<id>".
+        assert!(is_peer_allowed_path("/content"), "catalog must be allowed");
+        assert!(
+            is_peer_allowed_path("/content/abc123"),
+            "items must be allowed"
+        );
+        assert!(is_peer_allowed_path("/rpc/v1"));
+        assert!(is_peer_allowed_path("/health"));
+        // Not on the allow-list → rejected (no broad surface over the mesh).
+        assert!(!is_peer_allowed_path("/contention"), "must not prefix-leak");
+        assert!(!is_peer_allowed_path("/"));
+        assert!(!is_peer_allowed_path("/rpc/v2"));
+    }
+
     #[test]
     fn preserves_transitional_state_on_merge() {
         // existing: user initiated a stop, spawn_transitional set Stopping.