fix: use getAgentDisplayName in injectBoulderContinuation

The agent parameter was using raw config key "atlas" but the SDK
expects the display name "Atlas (Plan Executor)". This caused
"Agent not found: 'atlas'" errors when auto-compact tried to
continue boulder execution.

Root cause: injectBoulderContinuation passed raw agent key to
session.promptAsync, but SDK's agent matching logic compares
against display names registered in the system.

Fix: Use getAgentDisplayName() to convert the config key to
the expected display name before passing to the SDK.

src/hooks/atlas/boulder-continuation-injector.ts

@@ -2,6 +2,7 @@ import type { PluginInput } from "@opencode-ai/plugin"
 import type { BackgroundManager } from "../../features/background-agent"
 import { log } from "../../shared/logger"
 import { createInternalAgentTextPart, resolveInheritedPromptTools } from "../../shared"
+import { getAgentDisplayName } from "../../shared/agent-display-names"
 import { HOOK_NAME } from "./hook-name"
 import { BOULDER_CONTINUATION_PROMPT } from "./system-reminder-templates"
 import { resolveRecentPromptContextForSession } from "./recent-model-resolver"
@@ -62,7 +63,7 @@ export async function injectBoulderContinuation(input: {
     await ctx.client.session.promptAsync({
       path: { id: sessionID },
       body: {
-        agent: agent ?? "atlas",
+        agent: getAgentDisplayName(agent ?? "atlas"),
         ...(promptContext.model !== undefined ? { model: promptContext.model } : {}),
         ...(inheritedTools ? { tools: inheritedTools } : {}),
         parts: [createInternalAgentTextPart(prompt)],