write_bitcoin_conf silently produced an unpruned (~810GB and growing)
config regardless of disk: the framework node got a full-archive chain
on a 205GB volume. Volumes under 1.2TB now get prune = 25% of the
volume, clamped to [550MB, 100GB]; bigger volumes keep full archive;
unknown df results stay unpruned (don't surprise big iron). Framework
node switched live to prune=50000.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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