v0.17.1 — mounted packs work again

Fixed

Every pack published before engine 0.16 was unmountable through this server. It failed with no such column: synthesis_state — measured across the whole published pack line: 40 of 40 failed, 40 of 40 mount now.

The server exposes packs on top of the embedded engine (POST/GET /v1/packs/{digest}, GET /v1/pack-context, replicated mount), so the break was live here for anyone mounting a published pack.

The engine projected columns that a mounted pack's database cannot have and can never be migrated to get — it is opened read-only from a file another engine sealed, and the host's own database, which is always migrated, could never surface the problem. Engine 0.18.0 makes the projection schema-aware. Your .ydbpack files are unchanged and need no re-sealing.

Changed

• Engine pin 0.17.1 → 0.18.0, which also brings the pack substrate the endpoints can grow into: structured per-hit pack provenance, the signed retrieval settings on mounted_packs(), pack_context_for(pack_ids), and recall_from_packs_for(pack_ids, …) with the floor-as-a-wall rule.
• Server crate 0.17.0 → 0.17.1. No server API change.

Verification

All seven CI checks green including chaos-gate and the Windows leg; local suite green against 0.18.0 (356 + 350 + 13 + 6 + 4 + 2 + 2 passed, 0 failed); lockfile delta is exactly the engine swap.

What's Changed

• deps: engine v0.18.0; release v0.17.1 — mounted packs work again by @spranab in #99

Full Changelog: v0.17.0...v0.17.1