feat(agents): add ZWSP stable-sort prefixes for core agent list ordering

Populate AGENT_LIST_SORT_PREFIXES for sisyphus/hephaestus/prometheus/atlas
so the TUI agent list renders in canonical order. Update dependent tests
to use getAgentListDisplayName() instead of hardcoded display strings.

🤖 Generated with [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode) assistance

src/shared/agent-display-names.test.ts

@@ -181,17 +181,23 @@ describe("getAgentConfigKey", () => {
 })
 
 describe("getAgentListDisplayName", () => {
-  it("keeps sisyphus unchanged for list display", () => {
-    expect(getAgentListDisplayName("sisyphus")).toBe("Sisyphus (Ultraworker)")
+  it("applies invisible stable-sort prefixes to the core agent list", () => {
+    expect(getAgentListDisplayName("sisyphus")).toBe("\u200BSisyphus (Ultraworker)")
+    expect(getAgentListDisplayName("hephaestus")).toBe("\u200B\u200BHephaestus (Deep Agent)")
+    expect(getAgentListDisplayName("prometheus")).toBe("\u200B\u200B\u200BPrometheus (Plan Builder)")
+    expect(getAgentListDisplayName("atlas")).toBe("\u200B\u200B\u200B\u200BAtlas (Plan Executor)")
   })
 
-  it("returns atlas display name without sort prefix", () => {
-    expect(getAgentListDisplayName("atlas")).toBe("Atlas (Plan Executor)")
+  it("keeps non-core agents unprefixed for list display", () => {
+    expect(getAgentListDisplayName("oracle")).toBe("oracle")
   })
 })
 
 describe("normalizeAgentForPrompt", () => {
-  it("strips atlas UI ordering prefix back to canonical display name", () => {
+  it("strips core UI ordering prefixes back to canonical display names", () => {
+    expect(normalizeAgentForPrompt(getAgentListDisplayName("sisyphus"))).toBe("Sisyphus (Ultraworker)")
+    expect(normalizeAgentForPrompt(getAgentListDisplayName("hephaestus"))).toBe("Hephaestus (Deep Agent)")
+    expect(normalizeAgentForPrompt(getAgentListDisplayName("prometheus"))).toBe("Prometheus (Plan Builder)")
     expect(normalizeAgentForPrompt(getAgentListDisplayName("atlas"))).toBe("Atlas (Plan Executor)")
   })
 })

src/shared/agent-display-names.ts

@@ -20,7 +20,12 @@ export const AGENT_DISPLAY_NAMES: Record<string, string> = {
   "council-member": "council-member",
 }
 
-const AGENT_LIST_SORT_PREFIXES: Record<string, string> = {}
+const AGENT_LIST_SORT_PREFIXES: Record<string, string> = {
+  sisyphus: "\u200B",
+  hephaestus: "\u200B\u200B",
+  prometheus: "\u200B\u200B\u200B",
+  atlas: "\u200B\u200B\u200B\u200B",
+}
 
 function stripAgentListSortPrefix(agentName: string): string {
   return agentName.replace(/^\u200B+/, "")