refactor(scout-agent): only include compaction tool when warning is injected

The compact_conversation tool is now only available when the token
threshold is exceeded and the warning message is injected. This keeps
the tool list clean when compaction is not needed.

Updated tests to verify:
- Tool is NOT available when under threshold
- Tool IS available when warning is injected
- Tool is NOT available when compaction is disabled

Author: blink-so[bot]

packages/scout-agent/lib/core.test.ts

@@ -954,7 +954,7 @@ describe("coder integration", () => {
 });
 
 describe("compaction", () => {
-  test("buildStreamTextParams includes compaction tool by default", async () => {
+  test("buildStreamTextParams does not include compaction tool when under threshold", async () => {
     const agent = new blink.Agent<Message>();
     const scout = new Scout({
       agent,
@@ -973,8 +973,8 @@ describe("compaction", () => {
       model: newMockModel({ textResponse: "test" }),
     });
 
-    // Verify compaction tool is included
-    expect(params.tools[COMPACT_CONVERSATION_TOOL_NAME]).toBeDefined();
+    // Verify compaction tool is NOT included when under threshold
+    expect(params.tools[COMPACT_CONVERSATION_TOOL_NAME]).toBeUndefined();
   });
 
   test("buildStreamTextParams applies existing compaction summary", async () => {
@@ -1106,6 +1106,9 @@ describe("compaction", () => {
         m.content.includes("CONTEXT LIMIT WARNING")
     );
     expect(lastUserMessage).toBeDefined();
+
+    // Verify compaction tool IS available when warning is injected
+    expect(params.tools[COMPACT_CONVERSATION_TOOL_NAME]).toBeDefined();
   });
 
   test("buildStreamTextParams respects compaction: false to disable", async () => {
@@ -1136,8 +1139,8 @@ describe("compaction", () => {
       compaction: false,
     });
 
-    // Compaction tool should still be available (for manual use)
-    expect(params.tools[COMPACT_CONVERSATION_TOOL_NAME]).toBeDefined();
+    // Compaction tool should NOT be available when compaction is disabled
+    expect(params.tools[COMPACT_CONVERSATION_TOOL_NAME]).toBeUndefined();
 
     // No warning should be logged even with messages
     const warningLog = warnLogs.find((l) =>

packages/scout-agent/lib/core.ts

@@ -530,7 +530,7 @@ export class Scout {
     }
 
     const tools = {
-      ...createCompactionTool(),
+      ...(compactionWarningInjected ? createCompactionTool() : {}),
       ...(this.webSearch.config
         ? createWebSearchTools({ exaApiKey: this.webSearch.config.exaApiKey })
         : {}),