Alias Conversation instead of facading it; merge addAssistantMessage

A facade that forwards every method 1:1 is worse than paring the real type
down to the intended surface and aliasing it. conversation.Conversation's
interface is already the public surface we want (init/deinit, the
add*/replace* builders, and messages/allocator as plain data fields), so
public.zig now aliases it straight through and Agent.conversation() returns
a borrowed *Conversation for in-place surgery. Drops the ConversationData
alias and the pointer-wrapper.

Merged addAssistantMessageWithUsage into addAssistantMessage(blocks, ?usage)
on the real type (separate method deleted), so the alias has the intended
one-method shape; all call sites updated.

Only Agent and Stream remain true facades -- they have genuinely-internal
fields plus API-shaping renames (Stream.phase->state, Phase->State) an alias
can't express.

1 files changed, 5 insertions, 5 deletions

diff --git a/libpanto/src/anthropic_messages_json.zig b/libpanto/src/anthropic_messages_json.zig
index 940d55e..c2b133e 100644
--- a/libpanto/src/anthropic_messages_json.zig
+++ b/libpanto/src/anthropic_messages_json.zig
@@ -712,7 +712,7 @@ test "serializeRequest - signed assistant Thinking blocks round-trip" {
             .signature = sig,
         } },
         .{ .Text = try conversation.textualBlockFromSlice(allocator, "the answer is 42") },
-    });
+    }, null);
 
     const cfg = testConfig("claude-x");
     var empty_tools = tool_registry_mod.ToolRegistry.init(allocator);
@@ -755,7 +755,7 @@ test "serializeRequest - unsigned Thinking blocks are dropped" {
             .signature = null,
         } },
         .{ .Text = try conversation.textualBlockFromSlice(allocator, "answer") },
-    });
+    }, null);
 
     const cfg = testConfig("claude-x");
     var empty_tools = tool_registry_mod.ToolRegistry.init(allocator);
@@ -968,7 +968,7 @@ test "serializeRequest - dotted names are wire-encoded in tools and history" {
     try input.appendSlice(allocator, "{}");
     try conv.addAssistantMessage(&.{
         .{ .ToolUse = .{ .id = id, .name = name, .input = input } },
-    });
+    }, null);
 
     var tools = tool_registry_mod.ToolRegistry.init(allocator);
     defer tools.deinit();
@@ -1006,7 +1006,7 @@ test "serializeRequest - assistant ToolUse becomes tool_use content block" {
     try conv.addAssistantMessage(&.{
         .{ .Text = try conversation.textualBlockFromSlice(allocator, "calling tool") },
         .{ .ToolUse = .{ .id = id, .name = name, .input = input } },
-    });
+    }, null);
 
     var empty_tools = tool_registry_mod.ToolRegistry.init(allocator);
     defer empty_tools.deinit();
@@ -1144,7 +1144,7 @@ test "serializeRequest - empty ToolUse input becomes {} not invalid JSON" {
     const name = try allocator.dupe(u8, "noargs");
     try conv.addAssistantMessage(&.{
         .{ .ToolUse = .{ .id = id, .name = name, .input = .empty } },
-    });
+    }, null);
 
     var empty_tools = tool_registry_mod.ToolRegistry.init(allocator);
     defer empty_tools.deinit();