R1: move tool registry off Config onto Agent

The tool set is no longer part of the per-turn Config snapshot. Agent now
owns a ToolRegistry (created empty at init), populated via the new
Agent.registerTool / registerToolSource methods. openStream and
OpenStreamFn take the registry as an explicit parameter rather than reading
it from cfg.registry, so swapping provider/model between turns (setConfig)
no longer disturbs the tool set.

CLI migrated to register the Lua tool source onto the agent instead of a
locally-owned registry. Test harnesses updated to stage tools on the agent.

1 files changed, 7 insertions, 5 deletions

diff --git a/libpanto/src/provider.zig b/libpanto/src/provider.zig
index 0fe0ed4..8ea74f3 100644
--- a/libpanto/src/provider.zig
+++ b/libpanto/src/provider.zig
@@ -243,13 +243,14 @@ pub const ProviderStream = struct {
 /// `*const Config` between turns changes provider, model, base_url, and the
 /// visible tool set with no transport teardown.
 ///
-/// The tool registry is taken from `cfg.registry`; the serializers receive
-/// it directly. On success the caller owns the returned `ProviderStream` and
-/// must `deinit` it.
+/// The tool registry is supplied by the caller (the `Agent` owns it now,
+/// not `cfg`); the serializers receive it directly. On success the caller
+/// owns the returned `ProviderStream` and must `deinit` it.
 pub fn openStream(
     allocator: std.mem.Allocator,
     io: std.Io,
     cfg: *const config_mod.Config,
+    registry: *const ToolRegistry,
     conv: *conversation.Conversation,
     diag: ?*ProviderDiagnostic,
 ) anyerror!ProviderStream {
@@ -267,7 +268,7 @@ pub fn openStream(
                 .http_client = client,
                 .diag = diag,
             };
-            const rr = try req.open(conv, cfg.registry);
+            const rr = try req.open(conv, registry);
             return rr.providerStream();
         },
         .anthropic_messages => |*c| {
@@ -278,7 +279,7 @@ pub fn openStream(
                 .http_client = client,
                 .diag = diag,
             };
-            const rr = try req.open(conv, cfg.registry);
+            const rr = try req.open(conv, registry);
             return rr.providerStream();
         },
     }
@@ -291,6 +292,7 @@ pub const OpenStreamFn = *const fn (
     allocator: std.mem.Allocator,
     io: std.Io,
     cfg: *const config_mod.Config,
+    registry: *const ToolRegistry,
     conv: *conversation.Conversation,
     diag: ?*ProviderDiagnostic,
 ) anyerror!ProviderStream;