fix(copilot): mark internal hook injections as agent-initiated

Apply the internal initiator marker to automated continuation, recovery, babysitter, stop-hook, and hook-message injections so Copilot attribution consistently sets x-initiator=agent for system-generated prompts.

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

@@ -1,7 +1,7 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import type { BackgroundManager } from "../../features/background-agent"
 import { log } from "../../shared/logger"
-import { resolveInheritedPromptTools } from "../../shared"
+import { createInternalAgentTextPart, resolveInheritedPromptTools } from "../../shared"
 import { HOOK_NAME } from "./hook-name"
 import { BOULDER_CONTINUATION_PROMPT } from "./system-reminder-templates"
 import { resolveRecentPromptContextForSession } from "./recent-model-resolver"
@@ -53,7 +53,7 @@ export async function injectBoulderContinuation(input: {
         agent: agent ?? "atlas",
         ...(promptContext.model !== undefined ? { model: promptContext.model } : {}),
         ...(inheritedTools ? { tools: inheritedTools } : {}),
-        parts: [{ type: "text", text: prompt }],
+        parts: [createInternalAgentTextPart(prompt)],
       },
       query: { directory: ctx.directory },
     })