Shrink the any boundary: extend schema coverage, then promote no-explicit-any to error

[rebaserHEAD]

ESLint (PR #83) reports ~186 no-explicit-any warnings, deliberately left as warnings. Nearly all of them are the YAML ingest boundary: mapImporter internals, prototypeResolver, structural component handling. Hand-typing casts there would churn 200 sites without making anything safer.

The honest fix is the one started in PR #83: typed validation at the boundary (src/import/mapSchema.ts covers the map document shell), extended inward so downstream code inherits real types instead of any.

Sequence that makes sense:

• Chunk/tilemap/meta shapes inside mapImporter (typed by the existing schema, currently still traversed as any).
• Prototype shells in prototypeDiscovery (RawEntityPrototype & friends are honest interfaces already; the parse path just is not narrowed onto them).
• Component-editor payloads in componentEditors/.
• When the count is near zero, flip @typescript-eslint/no-explicit-any to error in eslint.config.js and remove the carve-out comment.

Same posture as the schema gate: type what the code actually assumes, never reject data the round-trip contract must preserve. The react-hooks v7 compiler diagnostics (also warn-only, see eslint.config.js) can ride along here — each one is either a documented-deliberate pattern to keep suppressed or a small refactor.