A successful compaction frees the largest allocation a long session ever
drops (the compressed-away message dicts), but Python's arena allocator
keeps those pages in the heap — RSS retains the pre-compaction
high-water mark until exit. #76905's trim_memory lifecycle covers the
gateway/TUI housekeeping loops but not the CLI compression path.
Call trim_memory(reason='post-compression') at the compression-success
point in ContextCompressor.compress(), following the house pattern
(lazy import in try, debug-level log on failure). The helper is
glibc-gated, config-gated and rate-limited, so it is a safe no-op on
other platforms and cannot fail compression.
Re-expresses the intent of #70782 (JonthanaHanh), which reached for a
bare gc.collect(); trim_memory is the house mechanism and already
wraps a collect.
kshitij