CCM-14750: Add release-check commit mappings - #301

Description

This slice adds commit-to-ticket mapping support for cases where a PR or commit carries the wrong Jira key.

It includes:

• support for loading commit-to-ticket overrides from a mapping file
• automatic detection of a .jira-commits file in the target repository root, with CLI override support
• comparison and fix-flow updates so mapped tickets are used consistently instead of the detected key
• reporting updates so mapped commits are visible and the mapped/detected ticket relationship is clear
• tests covering mapping-file parsing, override application, report rendering, and branch-specific validation

Context

NHS governance checks depend on the tool being able to represent the intended Jira ticket for the code being released. In practice, some PRs and commits carry the wrong issue number, which would otherwise make the governance report and any follow-up fixes misleading.

This slice makes the release-check tooling resilient to that data-quality problem by allowing explicit commit-level Jira overrides while keeping those overrides visible in the report output.

Why this is a separate slice

Although it touches reporting, the main concern here is semantic correction of commit-to-ticket matching. Splitting it from the surrounding roll-up work keeps the review focused on the new mapping contract, how it affects comparison/fix behaviour, and how the override is surfaced to operators.

Validation

• package install
• lint
• typecheck
• unit tests

Sensitive Information Declaration

• I confirm that neither PII/PID nor sensitive data are included in this PR and the codebase changes.