Optimize retained rendering and harden renderer state handling

[twme-ai]

Context

This is a reviewed replacement for #58. It contains every commit from #58 through 6dde5d0, plus the fixes found while reviewing and validating that PR as an integrated change.

The goal remains to reduce display-entity churn while making renderer state, CUI forwarding, commands, persistence, shared selections, and tests behave consistently.

Combined summary

Retained rendering and diagnostics

• Retain line shapes across render passes for cuboid, cylinder, ellipsoid, polygon, and polyhedron selections.
• Key retained lines by geometry and visual style so unchanged lines are reused, changed lines are replaced, and stale lines are removed.
• Keep fill faces and other transient shapes outside the retained pool so they are recreated cleanly.
• Track retained-line reuse, spawn, removal, line, and entity counts for debug output.
• Rebase display origins when the viewer moves far enough, with per-renderer error isolation and localized debug reporting.

Renderer and CUI state

• Centralize the decision for whether the server renderer should consume WorldEdit CUI packets.
• Preserve client-side CUI forwarding when the server renderer is disabled, while still handling Bedrock and particle fallback modes.
• Make outbound CUI parsing more defensive and avoid stream allocations in packet filtering paths.
• Implement CUI update events and mark affected selections dirty so retained renderers refresh correctly.
• Refresh renderer state after per-player settings and render-mode changes.

Commands, permissions, and persistence

• Refine permissions for render, share, view, label, list, and hide operations.
• Validate renderer setting names and values before applying them.
• Persist accepted share relationships and improve share/view cleanup behavior.
• Keep dirty player settings available for retry when a save fails instead of discarding unsaved state.
• Improve error logging and reload behavior for player settings and language/config state.

Shared selection lifecycle

• Generate deterministic shared-selection colors and retain color/component caches only while live renderer or label references exist.
• Keep TextDisplay and particle shared renderers aligned with active-share and view-all visibility.
• Remove stale renders and labels when a sharer becomes hidden, leaves loading distance, goes offline, loses its selection, changes world, or has missing player data.
• Apply particle max_render_distance and view-all distance rules both during normal viewer updates and during sharer-triggered push updates.
• Prevent cross-world TextDisplay shares and prevent push updates from recreating shared renders for viewers who disabled server rendering.
• Centralize single-viewer/single-sharer cleanup so text renderers, particle renderers, labels, colors, and component caches are released in the correct order.
• Clean label-only references and empty per-viewer maps, including sharer disconnect and view-all teardown paths.

Build, dependencies, and tests

• Update EntityLib to 3.3.4+b54a52a-SNAPSHOT as in Optimize retained line rendering and renderer state handling #58.
• Configure Maven Surefire 3.5.4, so the added JUnit 5 suite is actually discovered by the normal Maven lifecycle.
• Cover CUI parsing/forwarding, CUI updates, settings persistence, permission routing, share persistence, color parsing, and shared-cache cleanup.

Review fixes added after #58

• Fix the Maven configuration that previously reported a successful build while executing zero JUnit 5 tests.
• Allow users with only worldeditdisplay.use.view.hide to enter the view command route.
• Fix shared color/component cache leaks caused by releasing caches before removing the final label reference.
• Fix label-only references surviving viewer or sharer cleanup.
• Remove already-rendered view-all selections after they leave the configured loading distance.
• Make sharer-triggered updates obey the same distance, world, visibility, and renderer-enabled rules as normal viewer updates.
• Avoid removing the owning per-viewer map while an update pass is still using it.

Validation

• mvn -B clean verify (Paper): 30 tests, 0 failures/errors/skips; shaded JAR produced.
• mvn -B clean verify -Pspigot: 30 tests, 0 failures/errors/skips; shaded JAR produced.
• git diff --check: clean.

The existing Maven Shade warnings about overlapping EntityLib/annotation classes and resources remain unchanged and do not fail either build profile.

Supersedes #58.