fix(rpc-dll): bound diagnostic log growth

[ewrogers]

Summary

• cap each injected-client diagnostic log at 1 MiB
• keep lifecycle, connection, changed snapshot state, warnings, and failures
• suppress successful command noise and deduplicate repeated snapshot failures
• document the log policy and rotation behavior

Verification

• cargo test --workspace --all-features
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• native Windows i686 cargo test -p rpc-dll (240 passed)
• native Windows i686 Clippy with warnings denied
• mdbook build docs