Fix Talk Representation Workflow metadata and input cardinality

[witbrock]

Problem and change

Direct Talk Representation Workflow calls failed metadata validation before normalisation because all 11 optional inputs were declared mandatory. Mark those mappings optional and migrate only exact reviewed version-1 definitions to version2. Keep live customisations protected by the existing seed authority checks.

The reported request supplied a programme-level list of22 existing presentation IDs to this single-presentation workflow. Clarify the represented capability and reject that list when no singular presentation is selected, including when a workshop title is supplied, so it cannot accidentally create a new talk. Explicit per-presentation inputs and normal creation from a title remain supported. This repair does not perform the original source-recovery/batch enrichment.

Validation

• Reproduced the missing-context failure on unchanged code with an existing presentation ID.
  -148 affected talk, metadata and seed guard/invariant checks pass. One unrelated invariant expects canonical seed53 while main has54; identical failure reproduced on unchanged main.
• Full workflow replay covers sparse existing-ID input across all3 variants, repeat execution without additional concepts, title-only creation, batch rejection with/without a title, and version1-to2 migration/idempotent bootstrap.
• Live actor-scoped inspection found all23 original target records. Persisted trace failed at pre-action validation, before talk actions; no enrichment rerun performed. Live authority hashes match the reviewed version1 inputs.

Native task: #V#task_agent_d3c2e4f5158d3f96a11aa7b5a3df1794.