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/screens/new-workspace-screen.tsx

@@ -353,7 +353,6 @@ function submitWorkspaceDraft(input: SubmitDraftInput): void {
       attachments: attachments.filter(
         (attachment): attachment is UserComposerAttachment => attachment.kind !== "review",
       ),
-      cwd: workspaceDirectory,
     },
   });
   useWorkspaceDraftSubmissionStore.getState().setPending({
@@ -421,7 +420,6 @@ export function NewWorkspaceScreen({
   const draftKey = `new-workspace:${serverId}:${sourceDirectory}`;
   const chatDraft = useAgentInputDraft({
     draftKey,
-    initialCwd: sourceDirectory,
     composer: buildComposerConfig({
       serverId,
       isConnected,
@@ -751,7 +749,7 @@ export function NewWorkspaceScreen({
             onChangeText={chatDraft.setText}
             attachments={chatDraft.attachments}
             onChangeAttachments={chatDraft.setAttachments}
-            cwd={chatDraft.cwd}
+            cwd={sourceDirectory}
             clearDraft={handleClearDraft}
             autoFocus
             commandDraftConfig={composerState?.commandDraftConfig}