docs(solana-rpc): expand agave and geyser runbook

doc/step-002c-genesis-download-mainnet.txt

@@ -0,0 +1,34 @@
+Step 002C: Download genesis (mainnet) do /var/lib/solana/ledger (fix na "failed to open genesis")
+
+Objaw w logach:
+  Failed to load genesis_config ... missing genesis.bin
+  Extracting "/var/lib/solana/ledger/genesis.tar.bz2"...
+  Failed to start validator: failed to open genesis ... No such file or directory
+
+Fix:
+- Zaciagnij genesis archive na dysk i zrestartuj serwis.
+
+1) Zatrzymaj validator (zeby nie robil restart loop)
+  sudo systemctl stop agave-validator
+
+2) Pobierz genesis.tar.bz2 do ledger (jako user `solana`)
+  sudo -u solana -H bash -lc '
+    cd /var/lib/solana/ledger
+    rm -f genesis.tar.bz2 genesis.bin
+    curl -sSfL https://api.mainnet-beta.solana.com/genesis.tar.bz2 -o genesis.tar.bz2
+    ls -lh genesis.tar.bz2
+  '
+
+Oczekiwane:
+  - plik genesis.tar.bz2 istnieje (ok. kilkadziesiat KB)
+
+3) Start + logi
+  sudo systemctl start agave-validator
+  systemctl status agave-validator --no-pager -l
+  sudo journalctl -u agave-validator -n 80 --no-pager
+
+4) RPC check (local/WG)
+  curl -sS -H 'content-type: application/json' \
+    --data '{"jsonrpc":"2.0","id":1,"method":"getVersion"}' \
+    http://10.66.66.1:8899 | jq .
+