feat: v2.6 follow-ups — apps/server close-hook caller + DiffPanel staging hint (3.7)

apps/server fire-and-forgets BooCoder's Phase-3 close hooks (new coder-notify.ts, reuses BOOCODER_URL, never-rejects) on session-delete + chat archive/archive-all/delete, so warm backends + worktrees tear down immediately (idle-evict/reaper was the backstop). 3.7: BooCoder DiffPanel shows a muted one-liner when the selected provider can't see another agent's unapplied worktree edits (pure derivation from per-change agent + current provider, no new state). 6 new server tests (coder-notify); 537 server tests pass; web+server tsc/build clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/components/panes/CoderPane.tsx

@@ -388,12 +388,14 @@ function usePendingChanges(sessionId: string) {
 function DiffPanel({
   changes,
   loading,
+  currentProvider,
   onRefresh,
   onApprove,
   onReject,
 }: {
   changes: PendingChange[];
   loading: boolean;
+  currentProvider: string;
   onRefresh: () => void;
   onApprove: (id: string) => void;
   onReject: (id: string) => void;
@@ -409,6 +411,29 @@ function DiffPanel({
       ? `Changes from ${distinctAgents.map((a) => providerLabel(a)).join(', ')}`
       : null;
 
+  // v2.6 §9c: staging-boundary caveat. External agents (opencode/goose/qwen/
+  // claude) edit *inside their worktree*; native boocode reads/writes the
+  // *project root* via pending_changes. Unapplied edits don't cross that
+  // boundary. When the currently-selected provider can't see another side's
+  // staged-but-unapplied edits, surface a muted one-liner. agent===null
+  // (manual) is boundary-neutral. Pure derivation — no new state/fetch.
+  const isNativeProvider = currentProvider === 'boocode';
+  const boundaryHint = (() => {
+    if (isNativeProvider) {
+      // Native boocode is selected: it won't see external-worktree edits.
+      const external = distinctAgents.filter((a) => a !== null && a !== 'boocode');
+      if (external.length === 0) return null;
+      const who =
+        external.length === 1
+          ? providerLabel(external[0]!)
+          : external.map((a) => providerLabel(a)).join(', ');
+      return `${who}'s edits live in its worktree — BooCode won't see them until applied.`;
+    }
+    // An external agent is selected: it won't see boocode's project-root edits.
+    if (!distinctAgents.includes('boocode')) return null;
+    return `BooCode's edits live in the project root — ${providerLabel(currentProvider)} won't see them until applied.`;
+  })();
+
   return (
     <div className="flex flex-col h-full border-t border-border">
       <div className="flex items-center justify-between px-3 py-1.5 border-b border-border bg-muted/30">
@@ -430,6 +455,14 @@ function DiffPanel({
           {mixedNote}
         </div>
       )}
+      {boundaryHint && (
+        <div
+          className="px-3 py-1 border-b border-border bg-muted/10 text-xs text-muted-foreground"
+          title={boundaryHint}
+        >
+          {boundaryHint}
+        </div>
+      )}
       <div className="flex-1 overflow-y-auto">
         {pending.length === 0 ? (
           <div className="flex items-center justify-center h-full text-sm text-muted-foreground">
@@ -914,6 +947,7 @@ export function CoderPane({
           <DiffPanel
             changes={changes}
             loading={loading}
+            currentProvider={agentConfig.provider}
             onRefresh={refresh}
             onApprove={approve}
             onReject={reject}