chore(ci): replace mirror.yml with reusable wrapper (#23)

Pins to hyperpolymath/standards#187 merge SHA e6b2884722350515934d443daf23442f2195796f. Replaces the
canonical mirror.yml (~145 lines, drift-prone) with a thin ~13-line
wrapper. Forge selection still externalised to vars.<FORGE>_MIRROR_ENABLED.

Part of estate-wide convergence campaign 2026-05-26
(standards#199 / #187).

Author: hyperpolymath

.github/workflows/mirror.yml

@@ -1,73 +1,15 @@
 # SPDX-License-Identifier: MPL-2.0
-name: Mirror to GitLab and Bitbucket
+name: Mirror to Git Forges
 
 on:
   push:
-    branches: [main, master]
-    tags:
-      - 'v*'
+    branches: [main]
   workflow_dispatch:
 
 permissions:
   contents: read
 
 jobs:
-  mirror-gitlab:
-    runs-on: ubuntu-latest
-    permissions:
-      contents: read
-    if: ${{ vars.GITLAB_MIRROR_ENABLED == 'true' }}
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
-        with:
-          fetch-depth: 0
-
-      - name: Setup SSH
-        uses: webfactory/ssh-agent@a6f90b1f127823b31d4d4a8d96047790581349bd # v0.9.1
-        with:
-          ssh-private-key: ${{ secrets.GITLAB_SSH_KEY }}
-
-      - name: Add GitLab to known hosts
-        run: |
-          mkdir -p ~/.ssh
-          ssh-keyscan -t ed25519 gitlab.com >> ~/.ssh/known_hosts
-
-      - name: Push to GitLab
-        env:
-          REPO_NAME: ${{ github.event.repository.name }}
-        run: |
-          git remote add gitlab git@gitlab.com:hyperpolymath/${REPO_NAME}.git || true
-          git push gitlab HEAD:main --force || git push gitlab HEAD:master --force
-          git push gitlab --tags --force
-
-  mirror-bitbucket:
-    runs-on: ubuntu-latest
-    permissions:
-      contents: read
-    if: ${{ vars.BITBUCKET_MIRROR_ENABLED == 'true' }}
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
-        with:
-          fetch-depth: 0
-
-      - name: Setup SSH
-        uses: webfactory/ssh-agent@a6f90b1f127823b31d4d4a8d96047790581349bd # v0.9.1
-        with:
-          ssh-private-key: ${{ secrets.BITBUCKET_SSH_KEY }}
-
-      - name: Add Bitbucket to known hosts
-        run: |
-          mkdir -p ~/.ssh
-          ssh-keyscan -t ed25519 bitbucket.org >> ~/.ssh/known_hosts
-
-      - name: Push to Bitbucket
-        env:
-          REPO_NAME: ${{ github.event.repository.name }}
-        run: |
-          git remote add bitbucket git@bitbucket.org:hyperpolymath/${REPO_NAME}.git || true
-          git push bitbucket HEAD:main --force || git push bitbucket HEAD:master --force
-          git push bitbucket --tags --force
+  mirror:
+    uses: hyperpolymath/standards/.github/workflows/mirror-reusable.yml@e6b2884722350515934d443daf23442f2195796f
+    secrets: inherit