feat(atlas): update boulder continuation injector with lineage support

Update continuation injector to work with new lineage detection.
Refine idle event handling for proper subagent session tracking
and agent mismatch detection.

🤖 Generated with assistance of OhMyOpenCode

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

@@ -9,6 +9,8 @@ import { BOULDER_CONTINUATION_PROMPT } from "./system-reminder-templates"
 import { resolveRecentPromptContextForSession } from "./recent-model-resolver"
 import type { SessionState } from "./types"
 
+export type BoulderContinuationResult = "injected" | "skipped_background_tasks" | "skipped_agent_unavailable" | "failed"
+
 export async function injectBoulderContinuation(input: {
   ctx: PluginInput
   sessionID: string
@@ -21,7 +23,7 @@ export async function injectBoulderContinuation(input: {
   preferredTaskTitle?: string
   backgroundManager?: BackgroundManager
   sessionState: SessionState
-}): Promise<void> {
+}): Promise<BoulderContinuationResult> {
   const {
     ctx,
     sessionID,
@@ -42,7 +44,7 @@ export async function injectBoulderContinuation(input: {
 
   if (hasRunningBgTasks) {
     log(`[${HOOK_NAME}] Skipped injection: background tasks running`, { sessionID })
-    return
+    return "skipped_background_tasks"
   }
 
   const worktreeContext = worktreePath ? `\n\n[Worktree: ${worktreePath}]` : ""
@@ -61,7 +63,7 @@ export async function injectBoulderContinuation(input: {
 			sessionID,
 			agent: continuationAgent ?? agent ?? "unknown",
 		})
-		return
+		return "skipped_agent_unavailable"
 	}
 
 	try {
@@ -83,6 +85,7 @@ export async function injectBoulderContinuation(input: {
 
     sessionState.promptFailureCount = 0
     log(`[${HOOK_NAME}] Boulder continuation injected`, { sessionID })
+    return "injected"
   } catch (err) {
     sessionState.promptFailureCount += 1
     sessionState.lastFailureAt = Date.now()
@@ -91,5 +94,6 @@ export async function injectBoulderContinuation(input: {
       error: String(err),
       promptFailureCount: sessionState.promptFailureCount,
     })
+    return "failed"
   }
 }