Reduce routine eraser trace noise

[MRoiban]

Summary

• remove per-concrete-eraser success dumps from every state replay
• remove duplicate activation, queue, and deferred-success messages
• retain one compact replay summary with policy, size index, radius, and applied/seen tool counts
• retain all unavailable, mismatch, exception, and restricted-layer-change diagnostics
• reduce the bounded diagram observer budget from 60 to 6 and the generic eraser selection budget from 8 to 2

Validation

• make -C mods/custom-notebook-templates check
• clean NickelTC GCC 4.9.4/Qt 5.2.1 -Wall -Wextra -Werror build
• preview listener ABI verification
• loader-visible parity: 46 exports, 350 imports, and 9 ordered DT_NEEDED entries unchanged

This is intentionally post-release and does not change the v0.0.2-alpha tag or its verified installer.