cache knobs: env-parameterize geth/op-geth --cache (default 1024 = geth's own), l2geth --cache (default 8192 = previous hardcoded), nethermind MEMORYHINT (default 2048000000)

All defaults preserve current effective behavior - this deploy is a rendering no-op
until a host_var overrides a value. Part of the resource-optimizer knob rollout
(resource-optimizer/knob-manifest.yaml is the registry; verify_manifest.py enforces
default sync between templates and envfile).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

op/geth/mode-mainnet-op-geth-pruned-pebble-path.yml

@@ -57,6 +57,7 @@ services:
       - GETH_ROLLUP_SEQUENCERHTTP=https://mainnet.mode.network
     entrypoint: /bin/sh -c '[ -f /config/genesis.json ] && geth --db.engine=pebble --gcmode=full --datadir /data init --state.scheme=path /config/genesis.json; exec geth "$@"' --
     command:
+      - --cache=${MODE_MAINNET_OP_GETH_PRUNED_PEBBLE_PATH_CACHE:-1024}
       - --datadir=/data
       - --db.engine=pebble
       - --gcmode=full