fix: Handle panics when metadata references indices beyond array length

[0xikalgo]

Summary

The testnet API returns market metadata referencing token indices that exceed the token array bounds:

$ curl -s -X POST https://api.hyperliquid-testnet.xyz/info
   \                                                        
      -H 'Content-Type: application/json' \                 
      -d '{"type": "spotMeta"}' | jq '.tokens | length'     
1580   
                                                  
$ curl -s -X POST https://api.hyperliquid-testnet.xyz/info
   \                                                        
      -H 'Content-Type: application/json' \                 
      -d '{"type": "spotMeta"}' | jq '[.universe[].tokens[]]
   | max'                                                   
1827     

Markets like @1455 reference token index 1583, which doesn't exist in the 1580-element token array.

• Replace expect() with context() in spot_markets() when looking up base/quote tokens
• Replace direct array indexing with .get().context() in perp_markets() for collateral token lookup