P1 hardcoded the tech ids ("shipbuilding"/"ocean_navigation") in Rust — a Rail-2
violation (JSON is the canonical content store) and not single-source. Per owner
direction ("should be a player-level config setting"), the embark grant now lives
in data and is cached per player:
- mc_core::EmbarkLevel moves to the shared base crate (was mc-pathfinding) so
PlayerState can hold it; mc-pathfinding re-exports it. Adds from_mechanic_key
(the ONLY place the embark_* mechanic-key strings live).
- The naval techs carry the grant in JSON via unlocks.mechanics: shipbuilding →
embark_coast, ocean_navigation → embark_ocean. Which tech grants embark is now
authored data, not Rust.
- TechWeb::embark_level(researched) derives the strongest grant across a player's
researched techs (None < Coast < Ocean).
- PlayerState gains a cached embark_level field; process_science recomputes it
each turn from the researched set (idempotent → save-load / tech injection
covered). The move handler reads the cache (no per-move tech parsing).
Tests: mc-core EmbarkLevel ordering + mapping; mc-tech embark_level method
(inline web) + a real-data guard that authored naval.json carries the mechanics;
mc-pathfinding 9/9 unchanged. All green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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