Put releases back on merges to main

Restores the guard 7ddac38 replaced with `if: false`, so merging to main
bumps the patch version, uploads to PyPI with the existing PYPI_API_TOKEN
secret, and pushes the bump commit plus its tag. The guard matters: the
same workflow also fires on pull requests and a nightly schedule, and an
unguarded job would cut a release from both.

release.yml keeps building, smoke-testing and attesting every v* tag —
only its upload is switched off, so the tag stable.yml pushes cannot
start a second upload of a version PyPI already has. Going back to
tag-driven releases means registering a PyPI trusted publisher for
release.yml and swapping the two conditions.

Author: JE-Chen

.github/workflows/release.yml

@@ -56,6 +56,14 @@ jobs:
 
   publish:
     needs: build
+    # Publishing happens on merge to main (stable.yml), so this path stays
+    # off: the tags stable.yml pushes would otherwise start a second upload
+    # of a version PyPI already has. The build job above still runs on every
+    # v* tag — it verifies the tag matches pyproject, smoke-tests the wheel
+    # and attests provenance. To go back to tag-driven releases, register a
+    # PyPI trusted publisher for release.yml, drop this condition, and put
+    # stable.yml's publish job back behind `if: ${{ false }}`.
+    if: ${{ false }}
     runs-on: ubuntu-latest
     environment:
       name: pypi

.github/workflows/stable.yml

@@ -118,8 +118,12 @@ jobs:
 
   publish:
     needs: test
-    # Publishing moved to release.yml: immutable v* tags + Trusted Publishing.
-    if: ${{ false }}
+    # Releases ride on merges to main: this job bumps the patch version,
+    # uploads to PyPI with the PYPI_API_TOKEN secret, then pushes the bump
+    # commit (marked [skip ci]) and its v* tag. The guard is what keeps it
+    # off pull requests and the nightly schedule, which the same workflow
+    # also triggers on — without it every PR would cut a release.
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
     permissions:
       contents: write