Merge pull request #350 from input-output-hk/imp_makefile2
feat(makefile): harden venv activation checks
feat(makefile): harden venv activation checks
fix(tx): widen MempoolTxTooSlow retry backoff to 2-10s
Previous `uniform(0, r)` could sleep ~0s on early retries, too short to outlast GC pauses, snapshot writes, or CPU spikes that trigger the node's mempool wallclock soft-timeout. Use a flat 2-10s window and keep the latest error for the final exception chain.
Resolve symlinks when comparing $VIRTUAL_ENV to the project venv so a symlinked .venv path is recognized as activated. Add .check-venv-not-activated and gate clean-all on it to prevent removing a live venv. Route error messages to stderr.