chore: require a fee receiver at build time, ignore internal docs

The build now fails fast when KYBERSWAP_FEE_RECEIVER is unset instead of
shipping a bundle that sweeps output fees nowhere. Documents the key in
.env.example alongside what it actually costs: 0 bps on direct swaps, 9 bps
on ZAP's embedded swap leg.

Docs are written for the private tree and get copied in by mistake during a
sync, so *.md is ignored by default and publishing one is opt-in.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.env.example

@@ -1,7 +1,6 @@
 # LP TERMINAL — copy to `.env` in the REPO ROOT (next to package.json).
 # Vite reads it via envDir/envPrefix (see vite.config.ts); the indexer reads
-# `RPC` from the same file. Every key here is OPTIONAL — with no .env at all
-# the app runs against the chain's public RPC and the public Kyber aggregator.
+# `RPC` from the same file.
 
 # Private JSON-RPC URL for Robinhood Chain (chainId 4663), e.g. a provider URL
 # with its key path. SECRET: Vite BAKES this into the JS bundle, so set it only
@@ -10,19 +9,21 @@
 # Unset -> https://rpc.mainnet.chain.robinhood.com (keyless, slower).
 RPC=
 
-# KyberSwap aggregator base. Absolute URL = browser calls Kyber directly.
-# A path like /kyber = route through your own same-origin reverse proxy.
+# REQUIRED (the build fails without it): address that receives the terminal
+# output fee — currently 0 bps on direct swaps, 9 bps on ZAP's embedded swap
+# leg. Use an address you control. (Legacy env name.)
+KYBERSWAP_FEE_RECEIVER=
+
+# KyberSwap base for READ-ONLY USD valuation (UP rewards, APR, simulations).
+# MARKET and ZAP never call it, and the app has no Kyber transaction builder.
+# Absolute URL = browser calls Kyber directly; a path like /kyber = route
+# through your own same-origin reverse proxy.
 KYBERSWAP_AGGREGATOR_API_BASE_URL=https://aggregator-api.kyberswap.com
 KYBERSWAP_CHAIN=robinhood
 
-# WHITELIST: the only address swap calldata is ever sent to. The app hard-fails
-# a quote whose routerAddress differs from this. Change only if Kyber migrates.
-KYBERSWAP_ROUTER_ADDRESS=0x6131B5fae19EA4f9D964eAc0408E4408b66337b5
-
-# Optional platform fee on Kyber swaps, charged on the output token and paid by
-# the Kyber router. BOTH must be set to activate; leave blank for no fee.
-# KYBERSWAP_FEE_BPS=10
-# KYBERSWAP_FEE_RECEIVER=0x...
+# Swap-solver quote API (cross-venue split routing, ready-to-sign Settler tx).
+# Defaults to the hosted public instance; point it at your own if you run one.
+# VITE_SOLVER_URL=
 
 # Optional: only WalletConnect QR pairing needs this. Injected wallets
 # (MetaMask / Rabby / OKX) work without it. Get one at cloud.walletconnect.com