Rebuild world examples around Archetype World Libraries

[everettVT]

Summary

• replace the premature generic archetype_world framework with a concrete world_examples.biome domain package
• publish docs/world-libraries.md as the public engine/domain model and a grounded Biome walkthrough
• prove separate prefab-library and colony Worlds, durable placement rules, cross-World IsA provenance, cardinal power reconciliation, and powered mining
• add credential-free local Iceberg contract tests, an executable demo, and CI demo/build checks

Decisive behavior

Solar is a producer and conductor. Drill A can consume adjacent Solar power. Drill B touches Drill A but stays unpowered because demand does not imply conductivity. Adding a Pole extends the conductor network and powers Drill B. Only powered Drills mine.

Deliberate limits

• no second ECS, prefab layer, graph backend, or generic WorldLibrary engine API
• committed-change Observers are labeled as proposed; correctness uses explicit operations today
• cold-process verification is read-only because Archetype 0.5 does not expose complete public behavior-bundle reinstallation for mutable resume
• storage construction and migration remain Archetype and deployment responsibilities

Verification

• uv run ruff format --check .
• uv run ruff check .
• uv run pytest -q — 2 passed
• uv run python examples/biome.py
• uv build
• git diff --check