[Common] Command interface for authoritative state mutation - #58

Summary

Adds a closed Command variant and funnels authoritative tile and biome mutations through World::Apply.

Closes #27.

Why

World state mutations need a single application path that fires EnTT on_update notifications for future delta synchronization.

Type of change

• Gameplay or simulation logic
• Island generation, tile-map, or territory expansion
• Biome, resource, monster, or building rules
• Combat, quest, or exploration content
• Automation or resource-flow behavior
• Client UI, controls, camera, or player feedback
• Server, networking, persistence, or shared protocol
• Assets, content, balancing, or tuning
• Build, tooling, docs, or maintenance

Player-facing impact

None. This is an internal authoritative state-mutation interface.

World and biome impact

• Starting island generation: No behavioral change; generated chunks remain deterministic.
• Territory expansion blocks: N/A
• Biome distribution or selection: No generation change; explicit biome mutations now use commands.
• Resource availability: N/A
• Monster spawning: N/A
• Buildable structures: N/A
• Save/load compatibility: N/A

Technical notes

• Client impact: Formatting only; no behavior change.
• Server impact: Provides the authoritative command application surface; no server wiring in this PR.
• EnTT/ECS impact: Mutable registry access and public chunk lifecycle mutators are closed; accepted commands mutate through patch<Chunk> so on_update fires.
• CMake/vcpkg impact: None.
• Stacked PR base: world-generation.

How was this tested?

• CMake configure/build succeeded
• Tests passed locally, or missing tests are explained below
• vcpkg dependencies restore/install correctly
• Changed gameplay or simulation behavior was manually tested
• Tile, island, and territory expansion interactions still behave as expected
• Biome-specific resources, monsters, and buildings still behave as expected
• Client/server behavior was checked, if affected
• Save/load or persistence behavior was checked, if affected
• Performance was considered for large islands, expanded maps, or busy automation setups

Test details:

Windows x64 / Visual Studio 2026
cmake --preset debug
cmake --build --preset debug
ctest --test-dir out/build/debug --output-on-failure

Result: 1/1 tests passed.
Coverage includes command application, EnTT update notifications, seed/coordinate forwarding, and chunk load-order independence.

Screenshots or recordings

N/A

Checklist

• Documentation or README changes were added, if needed
• New dependencies, tools, assets, or configuration changes are documented
• Generated files, local-only settings, secrets, and credentials were not introduced
• Breaking changes, save migrations, or protocol changes are clearly described
• Review notes are included for risky or non-obvious changes