Chunksmith

A world-enter pregen that stopped early was recorded as having finished, and the world was then skipped forever. Reported on mod_support #35: a 5000-block radius produced a partial area, and on re-entry Chunksmith announced the world was already pre-generated and refused to run again. The resume-on-re-entry behaviour that makes a large radius workable at all was the exact thing being destroyed -- a 5000-block radius is about 306,000 chunks, which nobody finishes in one sitting.

Fixed

• The world-enter pregen treated "the task ended" as "the work finished". It recorded completion from GenerationCompleteEvent, which GenerationTask fires from the single end-of-task path that a genuine exhaustion of the iterator, a cancel, a pause and an auto-pause all reach. The task's own comment beside that line already said it: "Ending a task is not the same as finishing the work." Auto-pause is the likely trigger in the wild -- when the server cannot keep up, GenerationTask deliberately stops rather than stutter and expects the resume watcher to pick the run back up, which is correct behaviour and is not being changed here. What was wrong is that stopping made Chunksmith write worldenter-done.json with the configured radius, describing a run that had covered a fraction of it. WorldEnterDone.satisfies() then did its job perfectly and skipped that world on every subsequent load.
• Completion is now recorded only when the task itself reports the selection covered. The progress event already carries that verdict (GenerationTask.update() sets complete only when chunkIterator.total() - finishedChunks == 0), so the number being trusted is the task's own iterator total rather than this feature's estimateChunks() circle-area approximation -- which is documented as inexact and has no business deciding whether a permanent record gets written.
• The world is released either way. Whatever ended the task, the player is behind a frozen world and a progress screen, and leaving them there is the one outcome that is never acceptable. Only the permanent record is now conditional.
• The log stops lying. A run that ends short says how far it got, that it is deliberately not being recorded, that it will resume on the next load, and that an auto-pause above is the usual reason. It previously said "world-enter pregen finished; releasing the world. It will not run again on this world." on exactly this path, with a Task stopped line immediately above it.

Notes

• If a world is already stuck, it stays stuck until the record is removed -- this build cannot un-write what a previous one recorded. Delete <world>/chunksmith/worldenter-done.json, or raise worldEnterPregenRadius above the recorded value, and the feature re-arms.
• No change to auto-pause, to the radius, to the shape, or to the selection. The reported symptom of a square area is what a partial concentric run looks like: the pattern walks square rings outward from the centre, so a run that stops early leaves a filled square well inside the circular selection. That part was working as designed and only looked wrong because it had been declared finished.