feat(session): render streamed file mentions as cards

Break assistant text into stable blocks so streaming stays responsive and tool-created files surface as openable transcript cards instead of getting buried in prose.

pnpm-lock.yaml

@@ -85,6 +85,9 @@ importers:
       marked:
         specifier: ^17.0.1
         version: 17.0.1
+      remend:
+        specifier: ^1.3.0
+        version: 1.3.0
       solid-js:
         specifier: ^1.9.0
         version: 1.9.9
@@ -4454,6 +4457,9 @@ packages:
     resolution: {integrity: sha512-57frrGM/OCTLqLOAh0mhVA9VBMHd+9U7Zb2THMGdBUoZVOtGbJzjxsYGDJ3A9AYYCP4hn6y1TVbaOfzWtm5GFg==}
     engines: {node: '>= 12.13.0'}
 
+  remend@1.3.0:
+    resolution: {integrity: sha512-iIhggPkhW3hFImKtB10w0dz4EZbs28mV/dmbcYVonWEJ6UGHHpP+bFZnTh6GNWJONg5m+U56JrL+8IxZRdgWjw==}
+
   require-directory@2.1.1:
     resolution: {integrity: sha512-fGxEI7+wsG9xrvdjsrlmL22OMTTiHRwAMroiEeMgq8gzoLC/PQr7RsRDSTLUg/bZAZtF+TVIkHc6/4RIKrui+Q==}
     engines: {node: '>=0.10.0'}
@@ -9086,6 +9092,8 @@ snapshots:
 
   real-require@0.2.0: {}
 
+  remend@1.3.0: {}
+
   require-directory@2.1.1: {}
 
   require-in-the-middle@8.0.1: