fix: critical bugs, type corrections, RTDS race condition, and comprehensive test coverage

- Fix UpdateBalanceAllowance response not being unmarshaled (pkg/clob)
- Fix SignatureType enum collision: SignatureMagic and SignatureProxy both had value 1 (pkg/auth)
- Fix salt validation inconsistency: generation limited to 53 bits but validation allowed 63 bits (pkg/clob)
- Fix PriceHistoryPoint.Price type from string to float64 to match API response (pkg/clob/clobtypes)
- Fix RTDS subscribe race condition: subscribeRaw now waits for WebSocket connection before sending
- Add comprehensive tests for pkg/data (9.4% → 63.8%), pkg/ctf (11.6% → 71.1%),
  pkg/clob/ws (33.8% → 63.6%), pkg/rtds (35.0% → 62.1%), pkg/clob/rfq (38.5% → 100%),
  pkg/bridge (42.0% → 67.0%)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: dongowu

pkg/data/impl_test.go

@@ -52,8 +52,6 @@ func (d *staticDoer) Do(req *http.Request) (*http.Response, error) {
 
 func intPtr(v int) *int       { return &v }
 func int64Ptr(v int64) *int64 { return &v }
-func strPtr(v string) *string { return &v }
-func boolPtr(v bool) *bool    { return &v }
 
 func TestNewClientNilTransport(t *testing.T) {
 	// Should not panic with nil transport.