Reconcile a batch of local skills with the platform

One endpoint, two consumers:

• SDK auto-discovery (CI, agent boot): defaults are right. Send {"skills": [...]} and read created / updated / unchanged counts.
• Interactive CLI (decimalai skills sync ./skills/): pass response_mode="diff" to get a per-skill actions array including body_markdown for any skill where the remote version is newer (so the CLI can overwrite local files).

Conflict policy: with conflict_policy="newer_wins" (default), the side whose timestamp is later wins — best for human-in-the-loop CLI. For CI/SDK pipelines where the repo is the source of truth, pass conflict_policy="local_wins" to force every push. remote_wins is the inverse — useful for “treat the platform as canonical.”

Empty bodies are 422’d at Pydantic validation. Invalid names are 409’d at the same layer. Per-skill issues that survive validation (e.g. a transient DB error) land in the failures array; the rest of the batch still processes.

content_hash on each entry is optional — clients that already computed SHA-256 (CLI walking a directory) can pass it to save a server-side hash; clients that didn’t (SDK auto-discovery) can omit.