agent: use zenai's hasImage

zenai exports it now; drop the local copy and re-pin.

build.zig.zon

@@ -36,8 +36,8 @@
             .hash = "sqlite3-3.53.2-DMxLWuAOAAA_Px0arJOIOaP4AKEu5prbsQgPMA35W1zz",
         },
         .zenai = .{
-            .url = "git+https://github.com/lightpanda-io/zenai.git#b76da59f1b7c36d367a0914adf60a72ca6d87dd4",
-            .hash = "zenai-0.0.0-iOY_VEm3BgDBXrcf-iedI2lNaTE5oF7vyG0AxB85b-2q",
+            .url = "git+https://github.com/lightpanda-io/zenai.git#be5d2e70d3dcc9866041dbdbcfa1f18799601a30",
+            .hash = "zenai-0.0.0-iOY_VE23BgCNT-WtrAC6BM1J_G98bSk6kD0v8g09XWYA",
         },
         .isocline = .{
             .url = "git+https://github.com/arrufat/isocline?ref=lightpanda#832a9fe25f5f4458fcc47b5acc7c21db669c2f47",

src/agent/Conversation.zig

@@ -85,7 +85,7 @@ fn expireImages(self: *Conversation) void {
         const results = msg.tool_results orelse continue;
         var stripped: ?[]zenai.provider.ToolResult = null;
         for (results, 0..) |res, n| {
-            if (!hasImage(res.parts orelse continue)) continue;
+            if (!zenai.provider.hasImage(res.parts orelse continue)) continue;
             if (budget > 0) {
                 budget -= 1;
                 continue;
@@ -99,11 +99,6 @@ fn expireImages(self: *Conversation) void {
     }
 }
 
-fn hasImage(parts: []const zenai.provider.ContentPart) bool {
-    for (parts) |part| if (part == .image) return true;
-    return false;
-}
-
 /// Cap history growth: expire stale images, then once history exceeds
 /// `prune_high`, keep the system prompt plus the most recent `prune_keep`
 /// messages, snapped to a safe boundary so a tool_call isn't split from its