fix(agents): address all PR #2299 code review findings

Blocking fixes:
- B1: Return empty restrictions for unknown/custom agents instead of
  EXPLORATION_AGENT_DENYLIST, allowing custom agents full tool access
- B2: Use Object.create(null) consistently across all 5 agent-loading
  result objects to prevent prototype pollution
- B3: Add code comment documenting custom agent bash access trust model
- B4: Mock getOpenCodeConfigDir in opencode-config-agents-reader tests
  to prevent global config dir leakage

Non-blocking fixes:
- N1: Use resolveAgentDefinitionPaths with project boundary enforcement
  in opencode-config-agents-reader for path containment
- N2: Add session-scoped 30s TTL cache to resolveCallableAgents to
  avoid redundant SDK IPC calls per tool invocation
- N3: Extract shared parseToolsConfig into src/shared/parse-tools-config.ts
  replacing 4 duplicated local implementations
- N4: Add .min(1) to AgentDefinitionPathSchema rejecting empty paths
- N5: Add resolve-agent-definition-paths.test.ts covering tilde expansion,
  relative paths, boundary enforcement, and null containmentDir
- N6: Validate agent mode against allowed values instead of bare type
  assertion in opencode-config-agents-reader

src/tools/call-omo-agent/agent-resolver.test.ts

@@ -12,8 +12,8 @@
  * R6: No duplicate agent names in output
  * R7: Malformed agent entries (null, missing name, non-string name, whitespace-only) are skipped gracefully
  */
-const { describe, test, expect, mock } = require("bun:test")
-const { resolveCallableAgents } = require("./agent-resolver")
+const { describe, test, expect, mock, beforeEach } = require("bun:test")
+const { resolveCallableAgents, clearCallableAgentsCache } = require("./agent-resolver")
 const { ALLOWED_AGENTS } = require("./constants")
 
 function createMockClient(agents: Array<Record<string, unknown>>) {
@@ -33,6 +33,10 @@ function createFailingClient(error: Error = new Error("API unavailable")) {
 }
 
 describe("resolveCallableAgents", () => {
+  beforeEach(() => {
+    clearCallableAgentsCache()
+  })
+
   describe("#given the SDK returns agents successfully", () => {
     describe("#when only built-in agents exist", () => {
       test("#then every ALLOWED_AGENT appears in the result", async () => {

src/tools/call-omo-agent/agent-resolver.ts

@@ -8,20 +8,37 @@ type AgentInfo = {
   mode?: "subagent" | "primary" | "all";
 };
 
+const callableAgentsCache = new Map<string, { agents: string[]; timestamp: number }>();
+const CACHE_TTL_MS = 30_000;
+
+export function clearCallableAgentsCache(): void {
+  callableAgentsCache.clear();
+}
+
 /**
  * Resolves the set of callable agent names at execute-time by merging the
  * hardcoded `ALLOWED_AGENTS` with any additional agents discovered dynamically
  * via `client.app.agents()`. Custom agents loaded from registered agent
  * directories appear here alongside built-ins.
  *
+ * Results are cached per session for 30s to avoid redundant SDK IPC calls.
+ *
  * Falls back to `ALLOWED_AGENTS` alone if the dynamic lookup fails.
  *
  * @param client - The plugin client with access to the agent registry
+ * @param sessionId - Optional session ID for cache scoping
  * @returns Array of lowercase callable agent names (excludes primary-mode agents)
  */
 export async function resolveCallableAgents(
   client: PluginInput["client"],
+  sessionId?: string,
 ): Promise<string[]> {
+  const cacheKey = sessionId ?? "__default__";
+  const cached = callableAgentsCache.get(cacheKey);
+  if (cached && Date.now() - cached.timestamp < CACHE_TTL_MS) {
+    return cached.agents;
+  }
+
   try {
     const agentsResult = await client.app.agents();
     const agents = normalizeSDKResponse(agentsResult, [] as AgentInfo[], {
@@ -33,7 +50,9 @@ export async function resolveCallableAgents(
       .map((a) => a.name.trim().toLowerCase());
 
     const merged = new Set([...ALLOWED_AGENTS, ...dynamicAgents]);
-    return [...merged];
+    const result = [...merged];
+    callableAgentsCache.set(cacheKey, { agents: result, timestamp: Date.now() });
+    return result;
   } catch (error) {
     const message = error instanceof Error ? error.message : String(error);
     log(

src/tools/call-omo-agent/tools-edge-cases.test.ts

@@ -9,6 +9,7 @@
  */
 const { describe, test, expect, mock, beforeEach } = require("bun:test")
 const { createCallOmoAgent } = require("./tools")
+const { clearCallableAgentsCache } = require("./agent-resolver")
 
 type PluginInput = { client: any; directory: string }
 
@@ -50,6 +51,7 @@ const toolCtx = {
 }
 
 beforeEach(() => {
+  clearCallableAgentsCache()
   reserveSubagentSpawnMock.mockClear()
   reserveCommitMock.mockClear()
   reserveRollbackMock.mockClear()

src/tools/call-omo-agent/tools.test.ts

@@ -1,5 +1,6 @@
 const { beforeEach, describe, test, expect, mock } = require("bun:test")
 const { createCallOmoAgent } = require("./tools")
+const { clearCallableAgentsCache } = require("./agent-resolver")
 
 type PluginInput = { client: any; directory: string }
 type BackgroundManager = {
@@ -72,6 +73,7 @@ const toolCtx = {
 }
 
 beforeEach(() => {
+  clearCallableAgentsCache()
   assertCanSpawnMock.mockClear()
   reserveSubagentSpawnMock.mockClear()
   reserveCommitMock.mockClear()