Support alpha hotfix release versions (#34463)

## What changed

- Map Python `aN.postM` versions to Codex `-alpha.N.M` release tags through shared release-version helpers.
- Accept alpha hotfix versions in Python runtime workflows, Rust release validation, npm publishing, and the shell and PowerShell installers.

## Testing

- Cover version conversion, workflow output, runtime setup, artifact staging, and installer handling for alpha hotfix releases.

GitOrigin-RevId: b95edb56f7c93b435a8050c10f0202dc117e6669

.github/workflows/python-runtime-build.yml

@@ -4,7 +4,7 @@ on:
   workflow_call:
     inputs:
       runtime_version:
-        description: "Runtime version to build, for example 0.136.0 or 0.136.0a2."
+        description: "Runtime version to build, for example 0.136.0, 0.136.0a2, or 0.136.0a2.post1."
         required: true
         type: string
 
@@ -29,26 +29,9 @@ jobs:
           REQUESTED_RUNTIME_VERSION: ${{ inputs.runtime_version }}
         run: |
           set -euo pipefail
-          python3 - <<'PY'
-          import os
-          import re
-          from pathlib import Path
-
-          python_version = os.environ["REQUESTED_RUNTIME_VERSION"]
-          if match := re.fullmatch(r"([0-9]+\.[0-9]+\.[0-9]+)a([0-9]+)", python_version):
-              release_version = f"{match.group(1)}-alpha.{match.group(2)}"
-          elif re.fullmatch(r"[0-9]+\.[0-9]+\.[0-9]+", python_version):
-              release_version = python_version
-          else:
-              raise SystemExit(
-                  "Python runtime version must be stable or a numbered alpha, "
-                  f"for example 0.136.0 or 0.136.0a2; found {python_version}"
-              )
-
-          with Path(os.environ["GITHUB_OUTPUT"]).open("a") as output:
-              print(f"python_version={python_version}", file=output)
-              print(f"release_tag=rust-v{release_version}", file=output)
-          PY
+          python3 sdk/python/release_version.py \
+            "$REQUESTED_RUNTIME_VERSION" \
+            --github-output "$GITHUB_OUTPUT"
 
       - name: Download Python runtime release artifacts
         env: