frontend: validate the pipeline editor autosave entry with a zod schema

[SpicyPete]

Summary

Follow-up to #2624. The editor's crash-recovery buffer in localStorage was gated by a hand-written type guard that re-listed every field of EditorAutosaveEntry, so the type and the check had to be kept in step by hand. This replaces the guard with a zod schema and derives the type from it, so there is one definition of what a valid entry looks like.

• editorAutosaveEntrySchema pins version to AUTOSAVE_ENTRY_VERSION and keeps basedOnUpdateTime nullish, as before.
• readAll runs safeParse per entry and drops the ones that fail, so a stale or corrupt shape still can't reach form.reset.
• The only observable difference is that unknown keys on a stored entry are now stripped rather than carried along. Nothing reads them.

Testing

• rpcn-editor-autosave.test.tsx passes under the integration config.
• bun run type:check and Biome are clean on the changed file.

🤖 Generated with Claude Code

[github-actions]

✅ Clean — no registry drift, off-token colours, or ad-hoc classes

App: frontend · Scope: diff vs origin/master · Files: 1

	Count
⚠️ Outdated registry components	0
🛠 Locally-modified components	0
❓ Unknown to registry	0
🎨 Off-token palette colours	0
🔢 Ad-hoc utility classes	0

Generated by lookout audit-changes.