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.

2 files changed, 11 insertions, 19 deletions

diff --git a/src/main.zig b/src/main.zig
index ff00689..46b6320 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -365,21 +365,16 @@ pub fn main(init: std.process.Init) !void {
         );
     }
 
-    // The tool registry is owned here and referenced by the active config
-    // snapshot. Extensions register their tool source into it *after* the
-    // agent is built; the agent holds a `*const Config` pointing at this
-    // registry, so in-place registration before the first turn is visible.
-    var registry = panto.ToolRegistry.init(alloc);
-    defer registry.deinit();
-
     // Assemble the active configuration snapshot and build the agent now,
     // before luarocks bootstrap and extension loading. The agent adopts the
     // store (for free persistence) and the resumed conversation (or starts
-    // fresh). System-prompt seeding/reconciliation below runs *through* the
-    // agent so those entries persist.
+    // fresh). The agent owns its own tool registry (post-R1); extensions
+    // register their tool source onto it *after* the agent is built but
+    // before the first turn, so in-place registration is visible.
+    // System-prompt seeding/reconciliation below runs *through* the agent
+    // so those entries persist.
     const active_config: panto.config.Config = .{
         .provider = provider_config,
-        .registry = &registry,
         .compaction = compaction_cfg,
     };
     var agent = panto.agent.Agent.init(
@@ -468,7 +463,7 @@ pub fn main(init: std.process.Init) !void {
     std.log.debug("extensions: {d} tool(s) registered", .{n_ext_tools});
 
     if (n_ext_tools > 0) {
-        try registry.registerSource(rt.toolSource());
+        try agent.registerToolSource(rt.toolSource());
     }
 
     // Resolve the compaction system prompt (COMPACTION.md across layers,
diff --git a/src/system_prompt.zig b/src/system_prompt.zig
index b5423f8..6104034 100644
--- a/src/system_prompt.zig
+++ b/src/system_prompt.zig
@@ -467,12 +467,12 @@ fn openTmpSession(arena: Allocator, root: []const u8) !panto.session_manager.Ses
     return panto.session_manager.SessionManager.init(testing.allocator, testing.io, sessions, "/cwd");
 }
 
-/// Minimal agent harness for system-prompt tests: an empty registry and a
-/// throwaway provider config, wrapping a session store and (optionally) an
-/// adopted conversation. Holds the registry/config so the agent's borrowed
-/// pointers stay valid for the agent's lifetime.
+/// Minimal agent harness for system-prompt tests: a throwaway provider
+/// config wrapping a session store and (optionally) an adopted
+/// conversation. Post-R1 the agent owns its own (empty) tool registry, so
+/// the harness only holds the config to keep the agent's borrowed pointer
+/// valid for its lifetime.
 const SPAgentHarness = struct {
-    registry: panto.ToolRegistry,
     config: panto.config.Config,
     agent: panto.agent.Agent,
 
@@ -481,17 +481,14 @@ const SPAgentHarness = struct {
         store: panto.session_store.SessionStore,
         adopted: ?panto.conversation.Conversation,
     ) void {
-        self.registry = panto.ToolRegistry.init(testing.allocator);
         self.config = .{
             .provider = .{ .openai_chat = .{ .api_key = "k", .base_url = "u", .model = "m" } },
-            .registry = &self.registry,
         };
         self.agent = panto.agent.Agent.init(testing.allocator, testing.io, &self.config, store, adopted);
     }
 
     fn deinit(self: *SPAgentHarness) void {
         self.agent.deinit();
-        self.registry.deinit();
     }
 };