fix(composer): reconcile live-activity strip with the dock geometry from #3151

Post-rebase integration fixes after rebasing onto main, which landed the
composer dock geometry contract (PR #3151) in the same region this branch
reworks. The rebase kept main's dock architecture (reserved bottom rail +
ComposerActivityAccessory fade) with the branch's pill strip rendered
inside it; this commit cleans up the fallout:

- ChannelPane.tsx: re-add the useChannelWorkingAgentPubkeys import — the
  dock's reserved-rail toggle (composer-dock--with-activity) still needs
  the channel-level working-set check even though
  ChannelComposerActivityRow computes its own copy — and consolidate the
  gating into a single hasComposerBottomActivity expression
- ChannelComposerActivityAccessory.tsx: delete — main's channel-level
  wrapper from #3151 is fully superseded by ChannelComposerActivityRow
  rendered inside ComposerActivityAccessory
- AppShell.tsx / routes/root.tsx: move the temporary DebugHarnessMount
  from AppShell (999/1000 lines on main, so the mount no longer fits the
  file-size ratchet) to the root route via a RootComponent wrapper
- agents/debug/README.md + DebugHarnessMount.tsx: update the removal
  instructions and header comment for the new mount location

Validated with just desktop-check, 3,817 desktop unit tests, and the
channels / composer-overflow / threadpane-ultrawide e2e specs (88
passing).

Co-authored-by: Taylor Ho <taylorkmho@gmail.com>
Signed-off-by: Taylor Ho <taylorkmho@gmail.com>

desktop/src/features/channels/ui/ChannelComposerActivityAccessory.tsx

@@ -1,70 +0,0 @@
-import type { ComponentProps } from "react";
-
-import { CardMintComposerChip } from "@/features/agents/ui/CardMintComposerChip";
-import { useCardMintJobs } from "@/features/agents/cardMintStore";
-import { BotActivityComposerAction } from "@/features/channels/ui/BotActivityBar";
-import { ComposerActivityAccessory } from "@/features/messages/ui/ComposerActivityAccessory";
-import { TypingIndicatorRow } from "@/features/messages/ui/TypingIndicatorRow";
-
-type ChannelComposerActivityAccessoryProps = {
-  agents: ComponentProps<typeof BotActivityComposerAction>["agents"];
-  channel: ComponentProps<typeof TypingIndicatorRow>["channel"];
-  currentPubkey: ComponentProps<typeof TypingIndicatorRow>["currentPubkey"];
-  onOpenAgentSession: ComponentProps<
-    typeof BotActivityComposerAction
-  >["onOpenAgentSession"];
-  openAgentSessionPubkey: ComponentProps<
-    typeof BotActivityComposerAction
-  >["openAgentSessionPubkey"];
-  profiles: ComponentProps<typeof BotActivityComposerAction>["profiles"];
-  typingPubkeys: string[];
-  visible: boolean;
-  workingBotPubkeys: string[];
-};
-
-export function ChannelComposerActivityAccessory({
-  agents,
-  channel,
-  currentPubkey,
-  onOpenAgentSession,
-  openAgentSessionPubkey,
-  profiles,
-  typingPubkeys,
-  visible,
-  workingBotPubkeys,
-}: ChannelComposerActivityAccessoryProps) {
-  const cardMintJobs = useCardMintJobs();
-  return (
-    <ComposerActivityAccessory
-      className="px-5"
-      testId="channel-composer-activity-row"
-      visible={visible}
-    >
-      <div className="flex w-full items-center gap-2 overflow-visible pl-2">
-        {cardMintJobs.length > 0 ? <CardMintComposerChip /> : null}
-        {workingBotPubkeys.length > 0 ? (
-          <div className="flex min-w-0 flex-1 overflow-visible">
-            <BotActivityComposerAction
-              agents={agents}
-              channelId={channel?.id ?? null}
-              onOpenAgentSession={onOpenAgentSession}
-              openAgentSessionPubkey={openAgentSessionPubkey}
-              profiles={profiles}
-              workingBotPubkeys={workingBotPubkeys}
-              variant="inline"
-            />
-          </div>
-        ) : null}
-        {typingPubkeys.length > 0 ? (
-          <TypingIndicatorRow
-            channel={channel}
-            className="min-w-0 flex-1 py-0 pl-[calc(0.75rem+1px)] pr-0 sm:pl-[calc(1rem+1px)]"
-            currentPubkey={currentPubkey}
-            profiles={profiles}
-            typingPubkeys={typingPubkeys}
-          />
-        ) : null}
-      </div>
-    </ComposerActivityAccessory>
-  );
-}

desktop/src/features/channels/ui/ChannelPane.tsx

@@ -2,6 +2,7 @@ import * as React from "react";
 import { Hash, LogIn } from "lucide-react";
 import { AnimatePresence } from "motion/react";
 import { useAppNavigation } from "@/app/navigation/useAppNavigation";
+import { useChannelWorkingAgentPubkeys } from "@/features/agents/agentWorkingSignal";
 import { useMediaUpload } from "@/features/messages/lib/useMediaUpload";
 import { ComposerDockBackdrop } from "@/features/messages/ui/ComposerDockBackdrop";
 import { ComposerUploadProgressOverlay } from "@/features/messages/ui/ComposerUploadProgressOverlay";
@@ -399,18 +400,18 @@ export const ChannelPane = React.memo(function ChannelPane({
     !isComposerDisabled &&
     !isMainDeferredEditPending &&
     !isSinglePanelView;
-  const hasTypingActivity = typingPubkeys.length > 0;
-  // Unified working set for the composer bar: observer-derived turns primary,
-  // bot typing fallback (both folded together by agentWorkingSignal). This is
-  // what makes the bar show for an agent whose observer stream is live but
-  // whose typing signal never arrives — and vice versa.
+  // Working set for the composer bar (observer turns + bot-typing fallback,
+  // folded by agentWorkingSignal); gates the dock's reserved bottom rail.
   const composerWorkingBotPubkeys = useChannelWorkingAgentPubkeys(
     activeChannel?.id ?? null,
   );
-  const hasComposerBotActivity = composerWorkingBotPubkeys.length > 0;
+  // Background card mints surface in the same rail ("Minting card…" chip),
+  // so they must also reserve the activity row.
   const hasCardMintActivity = useCardMintJobs().length > 0;
   const hasComposerBottomActivity =
-    hasComposerBotActivity || hasTypingActivity || hasCardMintActivity;
+    composerWorkingBotPubkeys.length > 0 ||
+    typingPubkeys.length > 0 ||
+    hasCardMintActivity;
   const threadComposerBotTypingPubkeys = React.useMemo(() => {
     if (!openThreadHeadId) return [];
     return botTypingEntries
@@ -795,10 +796,9 @@ export const ChannelPane = React.memo(function ChannelPane({
                   }
                   showTopBorder={false}
                 />
-                {/* The activity accessory is anchored in the dock's reserved
-                    bottom rail, so fading it cannot change the observed
-                    overlay height or move the conversation. Its natural
-                    content height remains responsive. */}
+                {/* The accessory is anchored in the dock's reserved bottom
+                    rail, so fading it cannot change the observed overlay
+                    height or move the conversation. */}
                 <ComposerActivityAccessory visible={hasComposerBottomActivity}>
                   <ChannelComposerActivityRow
                     agents={activityAgents}
@@ -895,8 +895,7 @@ export const ChannelPane = React.memo(function ChannelPane({
                 )}
                 threadReplyUnreadCounts={threadReplyUnreadCounts}
                 activityAccessoryVisible={
-                  hasThreadComposerBotActivity ||
-                  threadTypingPubkeys.length > 0
+                  hasThreadComposerBotActivity || threadTypingPubkeys.length > 0
                 }
                 activityAccessoryContent={
                   hasThreadComposerBotActivity ||