Claude 4.5 Sonnet GA: programmatic tool calling + web_fetch + 1M-token context hit general availability

Anthropic's release notes for Claude 4.5 Sonnet document the GA promotion of three previously-beta capabilities: (1) programmatic tool calling — define a tool inside a code-execution sandbox and call it from the model; (2) web_fetch server tool with caching and provenance metadata; (3) 1M-token context window GA. Together these three GAs make Claude 4.5 Sonnet a credible default for long-context agent workloads that need tool use and live web grounding. Programmatic tool calling in particular replaces the brittle 'pre-generate JSON schema → model fills JSON → call API' loop with a sandbox-style execution model.