Adopt useActionLock in remaining double-submit-prone handlers

**This work depends on the work done in AI First epic #4848 and must be implemented after **

Follow-up to PR #4912. We extracted useActionLock
(assets/js/collaborative-editor/hooks/useActionLock.ts) from
TemplateBrowserModalWrapper's re-entrancy guard so double-submit protection
can be standardised across modals/handlers instead of drifting (see Stu's
review comment on #4912).

useActionLock wraps an async action with a synchronous useRef lock (so a
fast double-click can't slip through between render flushes), resets in a
single finally, and returns a useCallback-stable run plus an isPending
flag for disabling UI.

Not a fit for useRunRetry or the AI apply path - those locks aren't
promise-scoped and solve a different cross-user problem (noted in the hook's
doc comment).

Spots to bring in line as we touch them, roughly in priority order:

• components/GitHubSyncModal.tsx:73-78 - priority: Cmd/Ctrl+Enter
  calls handleSaveAndSync with no guard and the textarea is never
  disabled, so holding the shortcut fires concurrent save-and-syncs.
  User-reachable today.
• components/inspector/TemplatePublishPanel.tsx:78-140 - disable-only,
  no early-return guard; in create mode a double-fire of
  publish_template could create duplicate templates (nothing upserts
  it the way workflow saves are protected).
• components/inspector/trigger/TriggerEditWizard.tsx:89-95 - finish
  has no guard and the button isn't disabled during commit(), so a
  double-click double-commits.
• SelectedDataclipView.tsx:39-58 - lower risk, near-zero-cost to adopt.
• WorkflowSettings.tsx:81-99 - lower risk, near-zero-cost to adopt.

Each item can be its own small PR (swap manual flag/guard for
useActionLock), done opportunistically rather than as one big sweep.

Start with assets/js/collaborative-editor/hooks/useActionLock.ts, then inspect the listed handlers, prioritising components/GitHubSyncModal.tsx:73-78. Apply the hook to one handler at a time, preserving the existing action behavior and disabling its UI while pending; each item is complete when its handler cannot double-submit.