Add 'claude' provider alias, tighten CLI URL parsing, and improve start/send concurrency safety

[kubobeem]

Motivation

• Make the SDK compatible with Claude-style (Anthropic) workflows by accepting claude as a provider alias and normalizing it to anthropic across languages.
• Harden CLI URL parsing and validation to correctly handle bare ports, host:port, and HTTP/HTTPS forms and surface clear errors for invalid values.
• Fix race/visibility issues around client startup and Session.Send so concurrent starts and context cancellation behave correctly.

Description

• Added a new docs page docs/integrations/claude-code-compatibility.md and linked it from docs/index.md to document Claude/Anthropic compatibility.
• Normalized provider.type = "claude" -> "anthropic" in Go (normalizeProviderConfig), Node (normalizeProviderConfig), and Python (_convert_provider_to_wire_format) and extended provider types to include claude in Go/Node/Python type definitions.
• Strengthened CLI URL parsing in Go (parseCliUrl), Node (parseCliUrl), and Python (_parse_cli_url) to trim input, accept bare port numbers, prepend http:// for parsing, validate port ranges, and raise descriptive errors for invalid formats.
• Made Go Session.Send respect context cancellation by performing the RPC in a goroutine and selecting on ctx.Done(); updated SendAndWait to propagate context errors.
• Added concurrent-start deduplication in Node (startPromise) and Python (_start_task with _start_lock) so multiple simultaneous start() calls reuse a single startup flow.
• Minor import and comment updates to support the above changes and maintain consistent behavior across languages.

Testing

• Ran Go unit tests and build with go test ./... and the Go build which completed successfully.
• Ran Node checks including npm test/tsc and integration smoke flows which succeeded.
• Ran Python tests with pytest and basic runtime checks including type checks which passed.

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Codex Task