b8bc89c2f0
Review asked whether composing a preset per session compounds memory. Measured against the shipped compositions: it does not compound — growth is strictly linear at ~0.17 MB per agent on `minimal` and ~1.31 MB on `standard`, the first agent of a process pays ~7 MB more for module imports every later mount shares, and disposal returns essentially all of it. What the measurement did find is that nothing disposes. The api-proxy discards the handle it creates, archiving only edits the workspace registry, the registry has no eviction, and the sole disposal site in the host is the JSON-RPC server's shutdown. A preset did not introduce that; it raised the per-session price from ~0.2 MB to ~1.3 MB and made it visible. Recorded as a remaining TODO rather than fixed here: eviction belongs to the host that owns the handle, not to this seam.