blockrunai/blockrun-mcp

fix(polymarket) — reads and writes no longer share one RPC list. There was
a single POLYGON_RPC_URLS, and entry 0 doubled as the sole un-fallbacked
transport for every SIGNING wallet client (withdraw, redeem, relayer, setup).
So reordering what read like a read-only fallback list silently changed which
endpoint broadcasts every money transaction — a write-path change disguised as
a comment tweak, and one nobody would review as such. 0.32.4 documented the
hazard; this fixes it. POLYGON_READ_RPC_URLS keeps its fallback() chain;
POLYGON_WRITE_RPC_URL is a single endpoint, overridable with
POLYMARKET_WRITE_RPC_URL.

The write default is publicnode, not 1rpc — 1rpc answers once and then
returns -32001 "usage limit" (measured 2026-07-21), which is the last thing
you want broadcasting a withdrawal. And the write side is deliberately a single
endpoint rather than a fallback chain: viem's fallback() would re-send a
signed transaction to the next provider on a timeout, and a transaction the
first provider actually mined must not be broadcast twice. Failing loudly on
one endpoint is correct; silently retrying a money movement is not.

Credit to @KillerQueen-Z, who proposed splitting these in #66.

211 tests, typecheck, build and verify:prices (28/28) green.