fix(core): normalize tool schemas for Anthropic, add toolChoice=auto; feat(summon): agent definition support; docs: cc/ research findings

- registry.ts: add normalizeForAnthropic() to strip , additionalProperties, default, nullable from zodToJsonSchema output so Anthropic doesn't silently reject tool definitions
- agent.ts: add toolChoice=auto for Claude OAuth to prevent Opus thinking forever without calling tools
- summon.ts: add agentSlug parameter, build agents catalog in description, add toAvailableAgents helper
- agent-manager.ts: wire agent definition loading into spawnChildAgent, agent model fallback
- loader.ts: export loadAgent, expandAgentToolNames, getAgentDirPaths; add getAgentDirPaths for permission gate
- agent.ts: auto-allow read-only tools in agent definition directories
- packaging/PKGBUILD: exclude ARM64 prebuilds from x86_64 package
- cc/: research findings on Claude Opus tool calling issues
- tests: loader tests, summon tool tests

1 files changed, 17 insertions, 2 deletions

diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 1453a01..74cb159 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -2,7 +2,17 @@
 
 // Agent & LLM
 export { Agent } from "./agent/agent.js";
-export { deleteAgent, getAgentDirs, loadAgents, saveAgent } from "./agents/index.js";
+export {
+	deleteAgent,
+	expandAgentToolNames,
+	GLOBAL_AGENTS_DIR,
+	getAgentDirPaths,
+	getAgentDirs,
+	getProjectAgentsDir,
+	loadAgent,
+	loadAgents,
+	saveAgent,
+} from "./agents/index.js";
 // Chunk helpers
 export {
 	appendEventToChunks,
@@ -61,7 +71,12 @@ export { createToolRegistry } from "./tools/registry.js";
 export { createRetrieveTool, type RetrieveCallbacks } from "./tools/retrieve.js";
 export { BackgroundShellStore, createRunShellTool } from "./tools/run-shell.js";
 export { analyzeCommand } from "./tools/shell-analyze.js";
-export { createSummonTool, type SummonCallbacks } from "./tools/summon.js";
+export {
+	type AvailableAgent,
+	createSummonTool,
+	type SummonCallbacks,
+	toAvailableAgents,
+} from "./tools/summon.js";
 export { createTaskListTool, TaskList } from "./tools/task-list.js";
 export { clearSpillForTab } from "./tools/truncate.js";
 export { createWebSearchTool } from "./tools/web-search.js";