Add patch/post-rector links in bot comment; baseline change detection on posted build marker
### Problem/Motivation
Enhance bot comments with direct links to the generated rector patch and conditional post-rector analysis report. Replace change detection baseline with the last posted build's patch (from the results repo), eliminating spurious formatting noise from GitLab's interdiff reformatting and ensuring maintainers see only genuine rector output changes. Add shallow-clone tag fetching to support baseline lookups beyond the clone window, escape all dynamic values in git operations, and gate comment posting on change detection.
### Work items
- Commit(s): [6da38eb1a6](https://git.drupalcode.org/project/project_analysis/-/commit/6da38eb1a627), [c3119c7f8c](https://git.drupalcode.org/project/project_analysis/-/commit/c3119c7f8c72), [e3ecaadbc9](https://git.drupalcode.org/project/project_analysis/-/commit/e3ecaadbc979), [a368a4d76c](https://git.drupalcode.org/project/project_analysis/-/commit/a368a4d76c6a), [1b99a82059](https://git.drupalcode.org/project/project_analysis/-/commit/1b99a8205914), [2e5137894d](https://git.drupalcode.org/project/project_analysis/-/commit/2e5137894d00), [12d93413f9](https://git.drupalcode.org/project/project_analysis/-/commit/12d93413f984)
### Credit
- Implemented by: @bbrala
- Test-project feedback: @goba, @nicxvan, @wimleers, @rfay, @larowlan
---
*Filed retroactively as part of the Drupal 12 rector coverage effort. Closed as fixed; credit to be applied to the contributors listed above.*
*AI was used extensively to build this work and to file this issue. See [Dries Buytaert: AI-generated Rector rules for Drupal](https://dri.es/ai-generated-rector-rules-for-drupal) and [Björn Brala: Drupal Rector rules are config, not code. Mostly.](https://www.linkedin.com/pulse/drupal-rector-rules-config-code-mostly-bj%C3%B6rn-brala-vfpwe/).*
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