fix(app): source composer cwd from agent state, not draft hook

The GitHub picker showed "No results found." for any running agent after
the first message was sent. useAgentInputDraft owned a local cwd state
that clear("sent") wiped to "", so the composer read cwd: "" even though
the agent's real cwd was correct on the wire.

Drop cwd ownership from the hook. Composer takes cwd as a prop sourced
by the parent — agentState.cwd for running agents, composerState.workingDir
for drafts, sourceDirectory for setup flows. The hook now persists only
{text, attachments}. Legacy persisted drafts with a cwd field still
hydrate; tagged COMPAT(draft-cwd) for removal after 2026-11-09.

Also moves attachment pills back inside the composer's bordered surface
via a new attachmentSlot prop on MessageInput, and shrinks pill height
from 48 to 32 — the subagents-track tuck previously had attachments
floating between it and the input.

Adds one Playwright spec asserting the draft-create-agent path submits
the workspace cwd.

packages/app/src/panels/agent-panel.tsx

@@ -948,6 +948,7 @@ function ChatAgentContent({
   });
   if (nonReadyView) return nonReadyView;
   invariant(effectiveAgent, "effectiveAgent is defined when the non-ready view is absent");
+  invariant(agentState.cwd, "agent cwd is defined when agent content is ready");
 
   return (
     <View style={styles.root}>
@@ -977,7 +978,7 @@ function ChatAgentContent({
             isPaneFocused={isPaneFocused}
             isArchivingCurrentAgent={isArchivingCurrentAgent}
             archivedAt={agentState.archivedAt}
-            initialCwd={agentState.cwd ?? ""}
+            cwd={agentState.cwd}
             isSubmitLoading={showPendingCreateSubmitLoading}
             onAttentionInputFocus={attentionController.clearOnInputFocus}
             onAttentionPromptSend={attentionController.clearOnPromptSend}
@@ -1182,7 +1183,7 @@ function AgentComposerSection({
   isPaneFocused,
   isArchivingCurrentAgent,
   archivedAt,
-  initialCwd,
+  cwd,
   isSubmitLoading,
   onAttentionInputFocus,
   onAttentionPromptSend,
@@ -1195,7 +1196,7 @@ function AgentComposerSection({
   isPaneFocused: boolean;
   isArchivingCurrentAgent: boolean;
   archivedAt: Date | null;
-  initialCwd: string;
+  cwd: string;
   isSubmitLoading: boolean;
   onAttentionInputFocus: () => void;
   onAttentionPromptSend: () => void;
@@ -1218,7 +1219,7 @@ function AgentComposerSection({
       agentId={agentId}
       serverId={serverId}
       isPaneFocused={isPaneFocused}
-      initialCwd={initialCwd}
+      cwd={cwd}
       isSubmitLoading={isSubmitLoading}
       onAttentionInputFocus={onAttentionInputFocus}
       onAttentionPromptSend={onAttentionPromptSend}
@@ -1233,7 +1234,7 @@ function ActiveAgentComposer({
   agentId,
   serverId,
   isPaneFocused,
-  initialCwd,
+  cwd,
   isSubmitLoading,
   onAttentionInputFocus,
   onAttentionPromptSend,
@@ -1244,7 +1245,7 @@ function ActiveAgentComposer({
   agentId: string;
   serverId: string;
   isPaneFocused: boolean;
-  initialCwd: string;
+  cwd: string;
   isSubmitLoading: boolean;
   onAttentionInputFocus: () => void;
   onAttentionPromptSend: () => void;
@@ -1272,11 +1273,10 @@ function ActiveAgentComposer({
       serverId,
       agentId,
     }),
-    initialCwd,
   });
   const workspaceAttachmentScopeKey = useWorkspaceAttachmentScopeKey({
     serverId,
-    cwd: agentInputDraft.cwd,
+    cwd,
     workspaceId,
   });
   const workspaceAttachments = useWorkspaceAttachments(workspaceAttachmentScopeKey);
@@ -1326,7 +1326,7 @@ function ActiveAgentComposer({
         workspaceAttachments={workspaceAttachments}
         onOpenWorkspaceAttachment={handleOpenWorkspaceAttachment}
         onChangeAttachments={agentInputDraft.setAttachments}
-        cwd={agentInputDraft.cwd}
+        cwd={cwd}
         clearDraft={agentInputDraft.clear}
         autoFocus={isPaneFocused}
         isSubmitLoading={isSubmitLoading}