fix: show not deployed yet for undeployed apps in session preview tabs (#12076)

* fix: show not deployed yet for undeployed apps in session preview tabs

* fix: say what an embed-token 404 means in the app viewer comment

* fix: name the protection rule only when the rules were actually read

frontend/src/lib/components/apps/editor/InWorkspaceAppViewer.svelte

@@ -117,6 +117,9 @@
 			headers
 		})
 		if (!res.ok) {
+			// Minted for the deployed app under the caller's RLS: a 404 is "nothing deployed here" or
+			// "not visible to this member", the same reading as `getAppLiteByPath`'s 404 below.
+			if (res.status == 404) onLoadState?.('not_found')
 			const err: any = new Error('Failed to fetch embed token')
 			err.status = res.status
 			throw err

frontend/src/lib/components/sessions/ItemViewerView.svelte

@@ -21,8 +21,11 @@
 		previewLocationLabel,
 		barePath
 	} from './previewRouter'
-	import { useSessionPermissions } from './sessionPermissions.svelte'
+	import { useSessionPermissions, useSessionReadOnly } from './sessionPermissions.svelte'
 	import { agentWriteCount } from '$lib/components/flows/agentEditorStore.svelte'
+	import { userWorkspaces } from '$lib/stores'
+	import { findCanonicalDevWorkspace } from '$lib/utils/workspaceHierarchy'
+	import { devLabelNoun } from '$lib/utils/devWorkspaceLabel'
 
 	let {
 		runtime,
@@ -70,6 +73,8 @@
 		() => runtime.manager
 	)
 	const canEdit = $derived(permissions.canOpenEditor(kind))
+	const protectedWorkspace = useSessionReadOnly(() => workspaceId)
+	const devWorkspace = $derived(findCanonicalDevWorkspace(workspaceId, $userWorkspaces))
 
 	// This reads the deployed version over the API rather than from the editor cell the
 	// chat mutates, so it is the one preview kind that does not self-sync (the invariant
@@ -259,7 +264,11 @@
 			<div class="text-xs text-tertiary max-w-sm">
 				Nothing is deployed at <span class="font-mono">{path}</span>, so there is no deployed
 				version to view.{#if canEdit}{' '}
-					Deploy it from the editor to see it here.{/if}
+					Deploy it from the editor to see it here.{:else if protectedWorkspace.confirmed}{' '}
+					Direct deployment is disabled in this workspace, so this session can read and run deployed
+					items, but not edit. Pick {devWorkspace
+						? `its ${devLabelNoun(devWorkspace.dev_workspace_label)}`
+						: 'a fork'} to make changes.{/if}
 			</div>
 			{#if canEdit}
 				<Button unifiedSize="sm" variant="default" startIcon={{ icon: Pen }} on:click={toEditSide}>

frontend/src/lib/components/sessions/sessionPermissions.svelte.ts

@@ -16,9 +16,12 @@ import { previewPageAllowed, type PreviewPage } from './previewRouter'
 /** Whether a session in `workspace` is read-only because the workspace is protected: the verdict
  * `resolveSessionAccess` gives the chat, so the UI and the toolset agree. */
 export function useSessionReadOnly(workspace: () => string | undefined) {
-	const verdict = resource(workspace, async (ws) =>
-		ws ? { workspace: ws, readOnly: await isReadOnlySessionWorkspace(ws) } : undefined
-	)
+	const verdict = resource(workspace, async (ws) => {
+		if (!ws) return undefined
+		const readOnly = await isReadOnlySessionWorkspace(ws)
+		// Only a successful read settles a verdict; a failed one is read-only to fail closed.
+		return { workspace: ws, readOnly, rulesRead: settledReadOnlyVerdict(ws) !== undefined }
+	})
 	// `resource` keeps the previous workspace's verdict while it asks about the next one.
 	const verdictFor = (ws: string): boolean | undefined => {
 		const landed = verdict.current
@@ -38,6 +41,16 @@ export function useSessionReadOnly(workspace: () => string | undefined) {
 			const ws = workspace()
 			return !!ws && (verdictFor(ws) ?? false)
 		},
+		/** Protected by a rule that was actually read: false when the read failed, where the session
+		 * is still read-only. For text that names the rule as the reason. */
+		get confirmed() {
+			const ws = workspace()
+			if (!ws) return false
+			const landed = verdict.current
+			return landed?.workspace === ws
+				? landed.readOnly && landed.rulesRead
+				: (settledReadOnlyVerdict(ws) ?? false)
+		},
 		/** Whether the rules were read, a failed read included, which settles as read-only. */
 		get settled() {
 			const ws = workspace()