feat: add UserDraft.stopSync/restartSync, wire on script + low-code app /add init

frontend/src/lib/components/ScriptBuilder.svelte

@@ -100,6 +100,7 @@
 	import { buildForkEditUrl } from '$lib/utils/editInFork'
 	import OnBehalfOfSelector, { type OnBehalfOfChoice } from './OnBehalfOfSelector.svelte'
 	import WacExportDrawer from './scripts/WacExportDrawer.svelte'
+	import { UserDraft } from '$lib/userDraft.svelte'
 
 	let {
 		script = $bindable(),
@@ -343,6 +344,14 @@
 	let loadingSave = $state(false)
 
 	if (script.content == '') {
+		// Suspend autosave around the bootstrap mutations — seeding the
+		// editor with the template's `initialCode` is a programmatic
+		// write that shouldn't count as the user's "first edit" and
+		// shouldn't POST to the server. The route's UserDraft handle is
+		// keyed by `initialPath` (the URL path). Resumed in the async
+		// `.finally` so language switches AFTER bootstrap (which also
+		// call `initContent`) sync normally.
+		UserDraft.stopSync('script', initialPath)
 		if (template === 'wac_python') {
 			script.modules = {
 				'helper.py': {
@@ -358,7 +367,9 @@
 				}
 			}
 		}
-		initContent(script.language, script.kind, template)
+		initContent(script.language, script.kind, template).finally(() => {
+			UserDraft.restartSync('script', initialPath)
+		})
 	}
 
 	async function isTemplateScript() {

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

@@ -3,7 +3,7 @@
 
 	const bubble = createBubbler()
 	import SplitPanesWrapper from '$lib/components/splitPanes/SplitPanesWrapper.svelte'
-	import { getContext, onMount, setContext, untrack } from 'svelte'
+	import { getContext, onMount, setContext, tick, untrack } from 'svelte'
 	import { twMerge } from 'tailwind-merge'
 
 	import { Pane, Splitpanes } from 'svelte-splitpanes'
@@ -94,6 +94,15 @@
 
 	const appDraftPath = newApp ? '' : (path ?? '')
 	const appDraftHandle = inSessionPane ? undefined : UserDraft.use<App>('app', appDraftPath)
+	// Suspend autosave around mount — the route may have seeded `app`
+	// from an empty template (e.g. `/apps/add` redirect with
+	// `new_draft=true`), and the `firstMirror` effect below writes that
+	// seed into the handle as a programmatic mutation. Without
+	// suspension that write fires a POST that looks like the user's
+	// first edit before they've touched anything. `onMount`-then-`tick`
+	// resumes once all mount-time effects have settled, so the user's
+	// real first edit is the first POST.
+	if (appDraftHandle) UserDraft.stopSync('app', appDraftPath)
 	// Prefer the persisted autosave over the prop when both exist (e.g.
 	// /apps/add reload: the route always initializes `app` to an empty
 	// template, but the user's last session is sitting in LS under the
@@ -481,6 +490,14 @@
 	let mounted = false
 	onMount(() => {
 		mounted = true
+		// Resume autosave now that mount-time effects (the
+		// `firstMirror` mirror, prop-driven initialization, ...) have
+		// all run. `tick` waits for the current pending effect flush
+		// to complete so the post-suspend writes have been observed by
+		// the sync effect and silently dropped.
+		if (appDraftHandle) {
+			tick().then(() => UserDraft.restartSync('app', appDraftPath))
+		}
 
 		setTimeout(() => {
 			if ($initialized?.initialized === false) {

frontend/src/lib/userDraft.svelte.ts

@@ -117,6 +117,15 @@ type DraftEntry = {
 	 * incorrect POST.
 	 */
 	skipNextSync: boolean
+	/**
+	 * Sticky version of `skipNextSync`. While true, the reactive sync
+	 * effect updates the local state but never POSTs — used by callers
+	 * that programmatically mutate the draft as part of bootstrapping
+	 * (e.g. setting the editor's `initialCode` after mount) and don't
+	 * want those writes to land on the server as the user's "first
+	 * autosave". Toggled via `UserDraft.stopSync` / `restartSync`.
+	 */
+	syncSuspended: boolean
 	/**
 	 * Tears down the `$effect.root` scope that owns the entry's sync
 	 * effect. Called when the refcount hits 0. `undefined` only when the
@@ -410,6 +419,38 @@ export const UserDraft = {
 		UserDraft.discard(itemKind, path, undefined, opts)
 	},
 
+	/**
+	 * Suspend the reactive sync for `(workspace, itemKind, path)`.
+	 * Writes after this call still update the in-memory cell and any
+	 * subscribers but don't POST to the syncer. Use to bracket
+	 * programmatic mutations that happen during editor bootstrap (e.g.
+	 * seeding script content from `initialCode`, low-code app init)
+	 * so they don't appear on the server as the user's "first edit".
+	 *
+	 * The entry must already be live (acquired by `use`/`useMany`); a
+	 * no-op otherwise. Pair every `stopSync` with a `restartSync` —
+	 * forgetting to resume silently turns off autosave for the rest of
+	 * the session.
+	 */
+	stopSync(itemKind: UserDraftItemKind, path: string, opts?: UserDraftOptions): void {
+		const ws = resolveWorkspace(opts)
+		const entry = entries.get(mapKey(ws, itemKind, path))
+		if (entry) entry.syncSuspended = true
+	},
+
+	/**
+	 * Resume reactive sync for `(workspace, itemKind, path)` after a
+	 * `stopSync`. Subsequent writes that differ from the suspended-time
+	 * state are POSTed normally; writes made during the suspension are
+	 * dropped from the server's view (the local cell still reflects
+	 * them). No-op if the entry isn't live or wasn't suspended.
+	 */
+	restartSync(itemKind: UserDraftItemKind, path: string, opts?: UserDraftOptions): void {
+		const ws = resolveWorkspace(opts)
+		const entry = entries.get(mapKey(ws, itemKind, path))
+		if (entry) entry.syncSuspended = false
+	},
+
 	/**
 	 * List currently-mounted live entries for `workspace`. Without the
 	 * localStorage layer, "list" is meaningful only for in-tab entries —
@@ -649,6 +690,11 @@ function acquireEntry(
 				entry.skipNextSync = false
 				return
 			}
+			// `syncSuspended` swallows the POST but still advances
+			// `lastSerialized` (above) so when sync resumes the next
+			// real change is detected as a change — only the writes
+			// made during suspension are dropped from the server's view.
+			if (entry?.syncSuspended) return
 			void UserDraftDbSyncer.save({
 				workspace,
 				itemKind,
@@ -665,6 +711,7 @@ function acquireEntry(
 			path,
 			state: stateRef,
 			skipNextSync: false,
+			syncSuspended: false,
 			destroyRoot
 		})
 		return
@@ -680,7 +727,8 @@ function acquireEntry(
 		itemKind,
 		path,
 		state: fallback,
-		skipNextSync: false
+		skipNextSync: false,
+		syncSuspended: false
 	})
 }