Schema/clarify retry history

[Ma11hewThomas]

Summary

Clarifies how CTRF represents retry history.

This PR defines retryAttempts as the ordered history of attempts completed before the final attempt represented by the test object.

It addresses the retry-history ambiguity raised in #58.

Retry model

For a test executed N times:

• the test object represents the final attempt, N
• retryAttempts contains attempts 1..N-1
• the initial execution is included in retryAttempts when a retry occurs
• the final attempt is not duplicated in retryAttempts
• retries is the number of re-executions after the initial attempt
• retries equals retryAttempts.length
• the final attempt number is retries + 1
• the test object’s execution data describes the final attempt

Changes

• Adds terminology for initial, previous, final, and retry-history attempts
• Renames the retry-attempt object section to “Attempt History Entry Object”
• Clarifies executionId and attemptId semantics
• Defines ordering, numbering, and count requirements for retry history
• Requires non-negative retries and attempt durations
• Requires retryAttempts to be non-empty when present
• Updates the schema descriptions and embedded schema
• Corrects retry examples to remove duplicated final attempts
• Updates example test timing to represent the final attempt

Compatibility

This clarifies previously inconsistent specification text and examples.

Producers that currently include the final attempt in retryAttempts will need to exclude it and represent that attempt through the enclosing test object instead.

Related work

Addresses the retry-history portion of #58.