fix: schema inference not updating on reset and language switch (#8446)

Three root causes:

1. Editor.setCode() never dispatched `change` — it pre-set `code = ncode`
   before the Monaco edit, so the debounced updateCode() saw code == ncode
   and skipped dispatch. The Reset button, copilot accept, and other
   setCode callers never triggered schema inference. Fixed by capturing
   `changed` before the pre-set and dispatching directly when true.

2. EditableSchemaForm's $effect only tracked the schema reference, not
   its properties. Since inferArgs mutates schema in-place through the
   Svelte 5 proxy, the reference never changes and the effect never
   re-ran. Added schema?.order and Object.keys(schema?.properties ?? {})
   reads to detect in-place mutations (matching SchemaForm's pattern).

3. ScriptEditor's $effect depended on both selectedTab and code, causing
   a redundant double inferSchema call on every code change (racing with
   the on:change handler and initContent's explicit call). Moved code
   into untrack() so the effect only fires on tab switches.

Also removed the no-op `testPanelSchema = testPanelSchema` in
inferModuleSchema.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/EditableSchemaForm.svelte

@@ -297,7 +297,9 @@
 	}
 
 	const editTabDefaultSize = untrack(() => noPreview) ? 100 : 50
-	editPanelSize = untrack(() => editTab) ? (untrack(() => editPanelInitialSize) ?? editTabDefaultSize) : 0
+	editPanelSize = untrack(() => editTab)
+		? (untrack(() => editPanelInitialSize) ?? editTabDefaultSize)
+		: 0
 	let inputPanelSize = $state(100 - editPanelSize)
 	let editPanelSizeSmooth = tweened(editPanelSize, {
 		duration: 150
@@ -331,6 +333,10 @@
 		}
 	})
 	$effect(() => {
+		// Track schema properties and order so this effect re-runs when
+		// inferArgs rebuilds the schema (not just on reference change).
+		schema?.order
+		Object.keys(schema?.properties ?? {})
 		schema && untrack(() => onSchemaChange())
 	})
 	$effect(() => {

frontend/src/lib/components/Editor.svelte

@@ -347,7 +347,9 @@
 	}
 
 	export function setCode(ncode: string, noHistory: boolean = false): void {
-		if (code != ncode) {
+		// Track whether the code actually changed before updating.
+		const changed = code != ncode
+		if (changed) {
 			code = ncode
 		}
 
@@ -368,7 +370,13 @@
 				editor.pushUndoStop()
 			}
 		}
-		// Update lint diagnostics after code change
+		// Dispatch change immediately when code actually changed. This ensures
+		// callers like the Reset button and copilot trigger on:change handlers.
+		// The debounced onDidChangeModelContent handler will no-op since code
+		// will already match by the time it fires.
+		if (changed) {
+			dispatch('change', ncode)
+		}
 		updateRawAppLintDiagnostics()
 	}
 

frontend/src/lib/components/ScriptEditor.svelte

@@ -751,7 +751,6 @@
 		if (activeModuleTab === null) return
 		try {
 			await inferArgs(effectiveLang, editorCode, testPanelSchema)
-			testPanelSchema = testPanelSchema
 			moduleTestState[activeModuleTab] = { args: testPanelArgs, schema: testPanelSchema }
 		} catch (e) {
 			// Module code may be in-progress; silently ignore
@@ -1196,7 +1195,11 @@
 		!hasPreprocessor && (selectedTab = 'main')
 	})
 	$effect(() => {
-		selectedTab && code && untrack(() => inferSchema(code))
+		// Only depend on selectedTab (preprocessor ↔ main toggle).
+		// Code changes are handled by the editor on:change handler and
+		// explicit inferSchema calls (initContent, onMount), so we read
+		// `code` inside untrack to avoid a redundant double-inference race.
+		selectedTab && untrack(() => code && inferSchema(code))
 	})
 
 	let argsRender = $state(0)