ci: run tests on PRs to any branch, scope push trigger to dev/release

[ma-sadeghi]

Summary

• The Tests workflow currently only runs on PRs targeting release, so PRs into dev (including external PRs like Update numpy version constraint in pyproject.toml #3047) skip the full 3 Python × 3 OS matrix.
• Naively adding dev to the pull_request filter would double-fire CI for internal devs (push event + pull_request event on the same commits).
• Scope push: to just dev and release (long-lived branches), and let pull_request: handle every PR. Net: PRs into dev get the matrix, no duplicate runs on feature branches.

Behavior after this change

• Internal feature branch push → no CI yet
• Open PR (any base) → pull_request: runs the matrix once
• PR merges into dev or release → push: runs the matrix once
• External PR → pull_request: runs once

Test plan

• Confirm this PR itself triggers exactly one Tests matrix run via pull_request:
• After merge, confirm the push to dev triggers exactly one matrix run
• Confirm a follow-up push to a feature branch in PMEAL/OpenPNM does not trigger CI until a PR is opened

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.7%. Comparing base (78a83c8) to head (37cd2d6).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@          Coverage Diff          @@
##             dev   #3048   +/-   ##
=====================================
  Coverage   87.7%   87.7%           
=====================================
  Files        151     151           
  Lines       8879    8879           
=====================================
  Hits        7792    7792           
  Misses      1087    1087           

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