fix(workspace): one inert handle for aborted history and prompt-block mounts

An aborted parent no longer gets a separate never-called stub per method:
mountRecordedHistory returns its hoisted openRun (it answers false before
reading later state), and mountPromptBlocks returns one shared no-op for
update, setState, setTitle and dispose. This keeps the history.mjs and
prompt-blocks.mjs function-coverage floors (98) without lowering them.

Tests: test:coverage (Chromium and touch, 922 workflows) passes for all
61 files; it failed before on history.mjs 94.44 and prompt-blocks.mjs
93.75 function coverage.

web/js/workspace/history.mjs

@@ -31,7 +31,8 @@ function place(parent, node, before) {
 
 export function mountRecordedHistory(container, {api, positiveId, parentScope, sender, visit = {}, onParentRevalidate, onRecordedCount}) {
     const scope = createScope(), dispose = () => scope.dispose();
-    if (parentScope.signal.aborted) {dispose();return {dispose, openRun:() => false};}
+    // openRun is a hoisted declaration: on an aborted parent it answers false before reading any later state.
+    if (parentScope.signal.aborted) {dispose();return {dispose, openRun};}
     parentScope.signal.addEventListener('abort', dispose, {once:true});
     scope.cleanup(() => parentScope.signal.removeEventListener('abort', dispose));
     const section = el('section', undefined, 'library-surface recorded-history');

web/js/workspace/prompt-blocks.mjs

@@ -41,7 +41,9 @@ export function mountPromptBlocks(container, {prompts, sender, parentScope, role
     // The title is mutable so a saved title edited in place (setTitle below, #249 F1) renames the actions.
     let currentTitle = title || '';
     const actionName = (verb, role, rest = '') => `${verb} ${action(role)}${rest}${currentTitle ? `: ${currentTitle}` : ''}`;
-    if (parentScope.signal.aborted) return {update() {}, setState() {}, setTitle() {}, dispose() {}};
+    // An aborted parent gets one inert handle; every method is the same no-op.
+    const inert = () => {};
+    if (parentScope.signal.aborted) return {update:inert, setState:inert, setTitle:inert, dispose:inert};
     const scope = childScope(parentScope);
     container.classList.add('prompt-inspector');
     scope.listen(container, 'click', async event => {