Add tagpr configuration

[shamaton]

Summary

• Add tagpr workflow to automate release PR and tag creation.
• Configure tagpr for main, changelog generation, and v-prefixed tags.
• Exclude tagpr-labeled PRs from GitHub release changelogs.

Background / Motivation

Automates the release flow with tagpr so release PRs, changelogs, and tags can be managed consistently from the main branch.

Changes

• Add .github/workflows/tagpr.yml GitHub Actions workflow.
• Add .tagpr configuration with fixed major version 3.
• Add .github/release.yml changelog exclusion for the tagpr label.

Test Plan

• Not run; configuration-only change.

Notes

• The tagpr workflow runs on pushes to main.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.36%. Comparing base (5ec2f88) to head (12b4e58).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #63   +/-   ##
=======================================
  Coverage   98.36%   98.36%           
=======================================
  Files          72       72           
  Lines        6039     6039           
=======================================
  Hits         5940     5940           
  Misses         70       70           
  Partials       29       29           

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