Escalation alone only ratchets upward, so an opening bid that is too generous was
permanent: 0.60 of a 24 GB card for an engine that needs 0.25 is 8 GB no other model
could have. A successful boot states how much of the budget was left for the cache,
and `footprint = budget - cache` is the only direct measurement of an engine's real
cost there is — so it is now read back and used.

- _pump_logs captures "Available KV cache memory: N GiB" as it STREAMS. By the time the
  server answers its health check that line has scrolled out of the 80-line tail behind
  vLLM's route listing, so it cannot be recovered afterwards.
- On a boot with clear slack (> 1 GiB beyond the ~2 GiB target), a smaller share is
  computed from the measured footprint and recorded for the next start.
- The learned store is now a record per key, {"ok": booted, "failed": too small}, and
  the downward half may never propose a share at or below "failed" + a step. That floor
  is what stops it oscillating between a budget that works and one that does not.
- Over-provisioning now costs one boot instead of the life of the process, and the flat
  float format the previous version wrote still loads.

6 more tests (shrinking, the tight-fit no-op, the anti-oscillation floor, a missing
cache figure, the old format, and the footprint round-trip): 16 in the file, 255 across
the OCR/gate/cluster/remote-execution/placement files together.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0182DhR1eFNPQyGmDrpHbedY