merge: integrate origin/dev into modular-enforcement branch

Resolves all merge conflicts, preserving our split module structure
while integrating all dev changes:
- Custom agent summaries support (parseRegisteredAgentSummaries)
- Background notification queue (enqueueNotificationForParent)
- Atlas shared git-worktree module (collectGitDiffStats, formatFileChanges)
- Ralph-loop withTimeout + DEFAULT_API_TIMEOUT=5000
- Session recovery assistant_prefill_unsupported error type
- Atlas agentOverrides forwarding
- Config handler plan model demotion (buildPlanDemoteConfig)
- Delegate-task agentOverrides, promptSyncWithModelSuggestionRetry, variant
- LSP init timeout + stale init detection
- isPlanFamily function + task-continuation-enforcer hook
- Handoff command

src/hooks/session-recovery/hook.ts

@@ -81,11 +81,13 @@ export function createSessionRecoveryHook(ctx: PluginInput, options?: SessionRec
         tool_result_missing: "Tool Crash Recovery",
         thinking_block_order: "Thinking Block Recovery",
         thinking_disabled_violation: "Thinking Strip Recovery",
+        "assistant_prefill_unsupported": "Prefill Unsupported",
       }
       const toastMessages: Record<RecoveryErrorType & string, string> = {
         tool_result_missing: "Injecting cancelled tool results...",
         thinking_block_order: "Fixing message structure...",
         thinking_disabled_violation: "Stripping thinking blocks...",
+        "assistant_prefill_unsupported": "Prefill not supported; continuing without recovery.",
       }
 
       await ctx.client.tui
@@ -117,6 +119,8 @@ export function createSessionRecoveryHook(ctx: PluginInput, options?: SessionRec
           const resumeConfig = extractResumeConfig(lastUser, sessionID)
           await resumeSession(ctx.client, resumeConfig)
         }
+      } else if (errorType === "assistant_prefill_unsupported") {
+        success = true
       }
 
       return success