update later changes in template generator probably? #27

Issue #25 is: the engine should only catalog + render + payload. Disk belongs in markup-generator (writes already did; reads should too).

Two PRs:

1. markup-generator #275

New public helpers:

• pathExists(path)
• listTemplateFiles(dir, { skipFiles, extensions }) — missing dir → []

loadData / readJson / writeGeneratedFile were already here.

2. generate-template #26

• src/adapters/list-files.ts → listTemplateFiles from markup-generator
• src/adapters/payload-files.ts → loadData + pathExists
• generator.ts no longer imports node:fs
• No default dataDir probe. Missing payload throws NO_PAYLOAD unless you pass payload, dataPath, samplePayloads, loadPayload, or useDataFiles: true

Merge order: #275 → publish markup-generator → bump the dependency → merge #26.

Still later (issue PR C): move spawnSync file-renderer so render.ts is also fs-free. Not in these PRs.

Originally posted by @atherdon in #25