#110 Refresh signs on chunk load

[tpwalke2]

What

Detect and remove sign markers whose sign block no longer exists in the world when its chunk reloads — closing the last gap in stale-marker cleanup (issue #110).

Why

The existing removal mixin only fires for an in-game block change on a loaded chunk. A sign that vanishes any other way (external region-file deletion/regen, backup restore, manual NBT edit) leaves its cache entry and BlueMap marker orphaned forever. #109's region-sharded storage was built specifically so this follow-up would have something cheap to query against.

Changes

• SignChunkKey/SignChunkIndex (new, core/signs, plain Java) — chunk-granularity (16-block) lookup from chunk → tracked sign keys, so reconciliation never scans the full sign cache. Kept separate from the persistence-layer SignRegionKey (512-block region math is a file-layout concern, not a runtime lookup one).
• SignManager — maintains chunkIndex alongside the existing flat cache (add/remove/reload hooks); exposes getKeysInChunk(...).
• BlueMapSignMarkersMod — registers ServerChunkEvents.CHUNK_LOAD; on load, checks each tracked sign in that chunk still has a live SignBlockEntity, and removes (via the existing SignManager.remove) any that don't, logged at INFO since it signals an unattended/external change. Deliberately does not skip newly-generated chunks — that's exactly the "region file deleted externally" case this targets.
• Two plans/docs: the design plan for this feature, and an earlier reviewed-and-rejected refactor options doc for SignManager's in-memory storage (kept flat, per that doc's recommendation).
• No persistence/version bump — runtime-only change.

Testing

• ./gradlew test — new SignChunkKeyTest (12 cases) and SignChunkIndexTest cover chunk-boundary math and index add/remove/isolation/clear behavior.
• ./gradlew build — full build passes.
• Manual (./gradlew runServer, not automatable — touches live Minecraft/Fabric types):
  a. Place a sign, restart the server, confirm the marker is unchanged and no spurious removal is logged.
  b. Place a sign, stop the server, delete that sign's chunk region file (forces a regen) or remove the block via NBT editor, restart, walk into the chunk — confirm the INFO log line appears and the stale marker disappears from BlueMap.
  c. Repeat with signs in two dimensions at the same x/z to confirm dimension isolation.

[Copilot]

Pull request overview

This PR closes the stale-marker cleanup gap by reconciling tracked signs when their chunk loads: if a cached sign key no longer corresponds to a live SignBlockEntity in that chunk (e.g., chunk regen / external edits), the marker is removed using existing SignManager.remove(...) logic.

Changes:

• Add a chunk-granularity secondary index (SignChunkKey / SignChunkIndex) to map chunk → tracked SignEntryKeys for O(1) lookup.
• Update SignManager to maintain the chunk index alongside the existing flat signCache, and expose getKeysInChunk(...).
• Register ServerChunkEvents.CHUNK_LOAD to detect and remove stale markers on chunk load; add unit tests for the new index/key utilities.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/main/java/com/tpwalke2/bluemapsignmarkers/core/signs/SignChunkKey.java	Defines chunk key computation (16-block chunk math) for indexing signs by chunk.
src/main/java/com/tpwalke2/bluemapsignmarkers/core/signs/SignChunkIndex.java	Implements the chunk→keys index used to avoid scanning the full sign cache on chunk load.
src/main/java/com/tpwalke2/bluemapsignmarkers/core/signs/SignManager.java	Maintains the new chunk index during add/remove/reload and exposes chunk-key querying.
src/main/java/com/tpwalke2/bluemapsignmarkers/BlueMapSignMarkersMod.java	Hooks chunk-load event and removes tracked entries that no longer have a sign block entity.
src/test/java/com/tpwalke2/bluemapsignmarkers/core/signs/SignChunkKeyTest.java	Unit tests for chunk-key math (origin, boundaries, negative coords, dimension isolation).
src/test/java/com/tpwalke2/bluemapsignmarkers/core/signs/SignChunkIndexTest.java	Unit tests for index add/remove/query/clear behavior across chunks and dimensions.
plans/sign-storage-refactor-options.md	Documents why in-memory sign storage stays flat and evaluates alternative layouts.
plans/chunk-load-sign-reconciliation-plan.md	Design plan documenting the chunk-load reconciliation approach and performance constraints.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.