HttpBridge should classify timeouts and protocol errors with Bridge* errors

[bbopen]

Problem

HttpBridge throws generic Error for timeouts, network errors, and invalid JSON responses. This is inconsistent with NodeBridge/OptimizedNodeBridge, which use BridgeTimeoutError and BridgeProtocolError, making it harder to distinguish failure modes in callers.

Evidence

• src/runtime/http.ts: post() throws Error on non-OK responses; abort errors bubble as generic errors; invalid JSON returns raw text.

Acceptance criteria

• Map abort/timeouts to BridgeTimeoutError.
• Map invalid JSON/decoder failures to BridgeProtocolError.
• Preserve HTTP status code and body in error message.
• Add tests to validate error class and message content.

[bbopen]

Resolved by PR #150. BoundedContext.classifyError() maps timeout patterns to BridgeTimeoutError.