Add comment explaining why startup_wait is 300s

GitHub Actions environment can be very slow, requiring 5 minutes for
Solana localnet and Arcium MPC nodes to initialize. Local development
typically uses ~90s.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: mikemaccana

Anchor.toml

@@ -21,6 +21,8 @@ wallet = "~/.config/solana/id.json"
 test = "npx tsx tests/election.ts"
 
 [test]
+# GitHub Actions environment can be very slow - 300s (5 minutes) allows Solana localnet
+# and Arcium MPC nodes enough time to initialize. Local development typically uses ~90s.
 startup_wait = 300000
 shutdown_wait = 2000
 upgradeable = false