ci(python): drop PR labeled trigger for python-release dry-run

Remove the pull_request:[labeled] trigger from python-release.yml so the
workflow no longer fires (and shows a gray skipped check) when a PR gets any
non-dry-run label. The credential-free dry-run validation is now manual-only
(workflow_dispatch with publish=false), preserving the validation capability
without a PR gray segment.

- python-release.yml: on is workflow_dispatch only; build.if is
  github.event_name == 'workflow_dispatch'.
- ci-workflow.spec.ts: assert python-release has no pull_request event and the
  simplified build.if.
- python/development.(md,zh.md) and 2026-08-11-python-publication-workflow note
  (en/zh/i18n): describe the manual dispatch-only dry-run path.

Verification: ci-workflow.spec.ts 14/14, typecheck clean, note-format 585,
verify-translation-pairing consistent.

.github/workflows/python-release.yml

@@ -1,9 +1,9 @@
 name: Release (Python)
 
-# A PR labeled python-release-dry-run or a manual run with publish=false builds
-# and validates the complete release without registry credentials. Publication
-# is accepted only from a manual run on the matching python-v* tag when the
-# private publisher-repository identity and public-PyPI switch are configured.
+# A manual run with publish=false builds and validates the complete release
+# without registry credentials. Publication is accepted only from a manual run
+# on the matching python-v* tag when the private publisher-repository identity
+# and public-PyPI switch are configured.
 on:
   workflow_dispatch:
     inputs:
@@ -12,8 +12,6 @@ on:
         required: true
         type: boolean
         default: false
-  pull_request:
-    types: [labeled]
 
 permissions:
   contents: read
@@ -27,7 +25,7 @@ concurrency:
 jobs:
   build:
     name: Build four wheels
-    if: github.event_name == 'workflow_dispatch' || github.event.label.name == 'python-release-dry-run'
+    if: github.event_name == 'workflow_dispatch'
     uses: ./.github/workflows/build-exe-for-python-sdk.yml
     with:
       targets: node24-linux-x64,node24-linux-arm64,node24-macos-arm64