Suggestion: use ConnectorResponseSizeLimitError typed error (re: elastic/kibana#268591)

[jcger]

Context

This is a suggestion for elastic/kibana#268591 showing what the ConnectorAuthorizationError pattern would look like applied to the response size limit case.

What this adds

• ConnectorResponseSizeLimitError in kbn-connector-specs — a typed error with explicit limitBytes, contentLengthBytes, and estimatedOutputBytes fields, following the same shape as ConnectorAuthorizationError. Also adds a WeakMap-based setConnectorActionErrorMeta/getConnectorActionErrorMeta API so connector actions can annotate errors with provider-specific size hints before the executor processes them.
• responseSizeHeader on ActionDefinition — lets a connector declare which HTTP response header advertises the response size (defaults to content-length). The generated executor reads this header when a size-limit error occurs.
• get_axios_instance.ts — adds an Axios response interceptor that converts ERR_BAD_RESPONSE errors into ConnectorResponseSizeLimitError at the point the HTTP client aborts the stream.
• generate_executor_function.ts — catches ConnectorResponseSizeLimitError from the interceptor and rethrows it enriched with connector-specific metadata: the connector's declared responseSizeHeader value and any WeakMap-annotated hints from the action handler (e.g. Jina's x-decompressed-content-length).
• action_executor.ts — handles ConnectorResponseSizeLimitError in the catch block (parallel to the existing isConnectorAuthorizationError branch), serializing it into the action result as errorName: 'ConnectorResponseSizeLimitError' and structured errorMeta.
• ActionsResponseContentLengthLimitError in the workflow layer — a new ExecutionError subtype for when the Actions HTTP limit fires before the workflow step can enforce max-step-size. Gives actionable guidance including whether raising max-step-size would also raise the connector request limit.
• connector_step.ts — replaces the errorMsg.includes('maxContentLength') string-match with errorName === 'ConnectorResponseSizeLimitError' as the primary detection path. Routes to ResponseSizeLimitError when the workflow transport limit applies (i.e. http type, or spec connector with max-step-size), or to ActionsResponseContentLengthLimitError when the actions HTTP limit fired before the workflow could apply its own limit.
• ResponseSizeLimitError — extended to accept and surface contentLengthBytes and estimatedOutputBytes in the error message and details, including a suggested max-step-size value when one can be derived.

What this changes vs. the original PR

The cross-layer contract (actions plugin → workflow step) becomes explicit and typed instead of an untyped Record<string, unknown> bag detected by string-matching an internal Axios message. The old errorMsg.includes('maxContentLength') check is removed entirely; detection is now driven by errorName.