Summary

This adds an opt-in Render Loaded Chunk Edges performance option with three modes:

• Off: keeps Sodium's current full-neighborhood readiness behavior.
• Performance: renders eligible loaded edge chunks only after chunk loading has been quiet for a short cooldown.
• Immediate: renders eligible loaded edge chunks as soon as the center chunk has complete data and all known neighbors are complete.

The goal is to reduce visible holes at loaded chunk borders when the client already has the center chunk's block and light data, while keeping the conservative behavior as the default.

Background

This came out of a small standalone Fabric mod called EdgeChunkFix, which explored the same visual problem in the vanilla renderer. At loaded chunk borders, the client can sometimes select a block and know its state, but terrain rendering still leaves that block invisible because the renderer is stricter than the client-side world data.

That standalone mod is useful for vanilla-style rendering, but it is not compatible with Sodium because both alter terrain renderer behavior around LevelRenderer.cullTerrain. Integrating a Sodium-specific version here avoids that mod compatibility trap and makes the improvement available directly to Sodium users who choose to enable it.

This PR intentionally does not port the vanilla lighting workaround from that mod. It only adjusts Sodium's chunk readiness rule for the opt-in case.

Before / After

Before, client-known edge terrain can be selectable while the terrain itself is missing:

After, the already-known edge terrain renders:

Details

Sodium currently merges readiness across the 3x3 chunk neighborhood. If any neighboring chunk is absent, the merged status becomes empty, which can keep an otherwise complete center chunk out of the renderer.

With loaded-edge rendering enabled by mode:

• the center chunk still requires FLAG_HAS_BLOCK_DATA | FLAG_HAS_LIGHT_DATA
• known neighboring chunks must also have complete block and light data
• missing neighbors may be treated as absent context for the provisional edge mesh
• each ready chunk records a bitmask of which neighbors were missing when it became ready
• when chunk status changes, the changed chunk and its 3x3 neighborhood are re-evaluated
• if a ready chunk's missing-neighbor bitmask changes, the tracker queues a remove/add so the chunk is rebuilt with the new context

This means a mesh built while a neighbor was missing is not treated as final. Once the neighboring data arrives, the stored mask changes and the affected render chunk is rebuilt using the new neighbor data.

refreshReadyChunks() is the expensive path because it scans the tracked chunk map. It is used for global state changes such as option changes, view/load-distance context changes, and Performance mode entering or leaving its delayed edge-rendering state. Normal chunk status updates use local 3x3 updates unless Performance mode was actively rendering provisional edges and needs to globally disable them again after new chunk activity resumes.

Disabling the option restores the previous full-neighborhood readiness behavior.

Validation

• Built with ./gradlew :fabric:build --no-daemon on Minecraft 1.21.11/Fabric.
• Manually checked loaded/unloaded chunk border scenarios with the generated Fabric jar.