fix(delegate-task): use lowercase sisyphus-junior agent name in API calls

Previous fix (7ed7bf5c) only updated Atlas → atlas, but missed Sisyphus-Junior.
OpenCode does case-sensitive agent lookup, causing crash when delegate_task
tried to spawn 'Sisyphus-Junior' (registered as 'sisyphus-junior').

- SISYPHUS_JUNIOR_AGENT constant: 'Sisyphus-Junior' → 'sisyphus-junior'
- agent-tool-restrictions key: 'Sisyphus-Junior' → 'sisyphus-junior'
- Updated related test mocks

src/tools/delegate-task/tools.test.ts

@@ -288,7 +288,7 @@ describe("sisyphus-task", () => {
             id: "task-variant",
             sessionID: "session-variant",
             description: "Variant task",
-            agent: "Sisyphus-Junior",
+            agent: "sisyphus-junior",
             status: "running",
           }
         },
@@ -351,7 +351,7 @@ describe("sisyphus-task", () => {
             id: "task-default-variant",
             sessionID: "session-default-variant",
             description: "Default variant task",
-            agent: "Sisyphus-Junior",
+            agent: "sisyphus-junior",
             status: "running",
           }
         },
@@ -951,7 +951,7 @@ describe("sisyphus-task", () => {
             id: "task-unstable",
             sessionID: "ses_unstable_gemini",
             description: "Unstable gemini task",
-            agent: "Sisyphus-Junior",
+            agent: "sisyphus-junior",
             status: "running",
           }
         },
@@ -1016,7 +1016,7 @@ describe("sisyphus-task", () => {
             id: "task-normal-bg",
             sessionID: "ses_normal_bg",
             description: "Normal background task",
-            agent: "Sisyphus-Junior",
+            agent: "sisyphus-junior",
             status: "running",
           }
         },
@@ -1135,7 +1135,7 @@ describe("sisyphus-task", () => {
             id: "task-artistry",
             sessionID: "ses_artistry_gemini",
             description: "Artistry gemini task",
-            agent: "Sisyphus-Junior",
+            agent: "sisyphus-junior",
             status: "running",
           }
         },
@@ -1200,7 +1200,7 @@ describe("sisyphus-task", () => {
             id: "task-writing",
             sessionID: "ses_writing_gemini",
             description: "Writing gemini task",
-            agent: "Sisyphus-Junior",
+            agent: "sisyphus-junior",
             status: "running",
           }
         },
@@ -1265,7 +1265,7 @@ describe("sisyphus-task", () => {
             id: "task-custom-unstable",
             sessionID: "ses_custom_unstable",
             description: "Custom unstable task",
-            agent: "Sisyphus-Junior",
+            agent: "sisyphus-junior",
             status: "running",
           }
         },

src/tools/delegate-task/tools.ts

@@ -18,7 +18,7 @@ import { CATEGORY_MODEL_REQUIREMENTS } from "../../shared/model-requirements"
 
 type OpencodeClient = PluginInput["client"]
 
-const SISYPHUS_JUNIOR_AGENT = "Sisyphus-Junior"
+const SISYPHUS_JUNIOR_AGENT = "sisyphus-junior"
 
 function parseModelString(model: string): { providerID: string; modelID: string } | undefined {
   const parts = model.split("/")