Document the end-to-end ingest workflow

[underchemist]

Parent

#56

What to build

User-facing documentation for the new upload→ingest workflow.

• Update the ingest example notebook to show the full flow: parse an IngestSpec, stage local source file sets with with_uploaded_sources, then create / await / start the ingestion under LiveStatus.
• Add IngestSpec to the API reference (autodoc).
• Document the auth constraint (the workflow requires OAuth/IDP; not supported in API-key mode) and how destination prefixes are composed (prescient_upload_prefix plus a per-location uuid).
• Ensure the glossary (CONTEXT.md) terms — ingestion specification, IngestSpec, location, source file set, staging — stay consistent with the shipped API.

Acceptance criteria

• Ingest example notebook demonstrates from_file → with_uploaded_sources → create → wait/start
• IngestSpec appears in the rendered API docs
• Auth constraint and prefix-composition behavior are documented
• Glossary terms match the shipped API surface

Blocked by

• End-to-end staging: IngestSpec.with_uploaded_sources #61