docs: constrain verbose Java process output

[SirEdvin]

Summary

• keep full Java, Minecraft, loader, Gradle, and installer logs on disk
• return only compact readiness, failure, count, timing, and shutdown evidence to agents
• prefer completion/readiness notifications over repeated polling
• batch expensive runtime validation where practical

Why

A recent Minecraft migration audit found about 278k direct tokens of Java-process output across agent sessions. In one OpenCode session, retained Java logs caused about 5.2M cumulative input-token exposures. A truncated 50 KiB log still cost roughly 15k tokens while omitting useful context.

Validation

• git diff --check
• documentation-only change