Add Cloudflare Pages docs preview with /preview-docs slash command

.github/workflows/docs-preview-cleanup.yml

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+name: Docs Preview Cleanup
+
+# Deletes Cloudflare Pages preview deployments for a PR when it closes.
+# Runs as pull_request_target so secrets are available for fork PRs; it never
+# checks out PR code, so there is no untrusted-code execution risk.
+
+on:
+  pull_request_target:
+    types: [closed]
+
+permissions: {}
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Delete preview deployments for this PR
+        env:
+          CF_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          CF_ACCOUNT_ID: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
+          CF_PROJECT: ${{ vars.CLOUDFLARE_PAGES_PROJECT }}
+          BRANCH: pr-${{ github.event.pull_request.number }}
+        run: |
+          set -euo pipefail
+          if [ -z "$CF_API_TOKEN" ] || [ -z "$CF_ACCOUNT_ID" ] || [ -z "$CF_PROJECT" ]; then
+            echo "Cloudflare credentials/project not configured; skipping cleanup."
+            exit 0
+          fi
+          base="https://api.cloudflare.com/client/v4/accounts/$CF_ACCOUNT_ID/pages/projects/$CF_PROJECT/deployments"
+          # Collect matching ids across all pages first, then delete — deleting
+          # mid-pagination would shift later pages and skip entries.
+          ids=""
+          for page in $(seq 1 50); do
+            resp=$(curl -fsS -H "Authorization: Bearer $CF_API_TOKEN" "$base?env=preview&per_page=25&page=$page")
+            ids="$ids $(jq -r --arg b "$BRANCH" '.result[]? | select(.deployment_trigger.metadata.branch == $b) | .id' <<<"$resp")"
+            [ "$(jq '.result | length' <<<"$resp")" -lt 25 ] && break
+          done
+          deleted=0
+          for id in $ids; do
+            echo "Deleting deployment $id"
+            curl -fsS -X DELETE -H "Authorization: Bearer $CF_API_TOKEN" "$base/$id?force=true" > /dev/null
+            deleted=$((deleted + 1))
+          done
+          echo "Deleted $deleted deployment(s) for $BRANCH."

.github/workflows/docs-preview.yml

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+name: Docs Preview
+
+# Builds the mkdocs site for a PR and deploys it to Cloudflare Pages.
+#
+# Security: mkdocs executes Python from the PR (mkdocstrings imports src/mcp,
+# `!!python/name:` directives). The build is gated by `authorize` (admin sender
+# for auto-preview, admin/maintainer commenter for /preview-docs) and isolated
+# from Cloudflare secrets — `build` runs PR code with no secrets and hands the
+# static site to `deploy` via an artifact, so PR code never shares a runner
+# with the Cloudflare token.
+#
+# Required configuration:
+#   - secrets.CLOUDFLARE_API_TOKEN   (scope: Account → Cloudflare Pages → Edit)
+#   - secrets.CLOUDFLARE_ACCOUNT_ID
+#   - vars.CLOUDFLARE_PAGES_PROJECT  (existing Pages project, e.g. mcp-python-sdk-docs)
+
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronize]
+    paths:
+      - docs/**
+      - docs_src/**
+      - mkdocs.yml
+      - pyproject.toml
+  issue_comment:
+    types: [created]
+
+permissions: {}
+
+concurrency:
+  group: docs-preview-pr-${{ github.event.pull_request.number || github.event.issue.number }}
+  cancel-in-progress: true
+
+jobs:
+  authorize:
+    if: >-
+      github.event_name == 'pull_request_target' ||
+      (github.event.issue.pull_request && startsWith(github.event.comment.body, '/preview-docs'))
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: read
+    outputs:
+      authorized: ${{ steps.check.outputs.authorized }}
+      pr_number: ${{ steps.check.outputs.pr_number }}
+      head_sha: ${{ steps.check.outputs.head_sha }}
+      slash_attempt: ${{ steps.check.outputs.slash_attempt }}
+    steps:
+      - name: Determine authorization
+        id: check
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
+        with:
+          script: |
+            const { owner, repo } = context.repo;
+
+            async function permissionFor(username) {
+              const { data } = await github.rest.repos.getCollaboratorPermissionLevel({ owner, repo, username });
+              return { level: data.permission, role: data.role_name };
+            }
+
+            let authorized = false;
+            let prNumber = '';
+            let headSha = '';
+            let slashAttempt = false;
+
+            if (context.eventName === 'pull_request_target') {
+              // Gate on the *sender* (whoever caused this run — on synchronize that
+              // is the pusher), not the PR author, so a non-admin pushing to an
+              // admin-opened branch does not get an automatic build.
+              const actor = context.payload.sender.login;
+              prNumber = String(context.payload.pull_request.number);
+              headSha = context.payload.pull_request.head.sha;
+              const perm = await permissionFor(actor);
+              authorized = perm.level === 'admin';
+              core.info(`pull_request_target by ${actor} (level=${perm.level}, role=${perm.role}) → authorized=${authorized}`);
+            } else {
+              // issue_comment: the job-level `if:` already guarantees this is a PR
+              // comment starting with /preview-docs.
+              slashAttempt = true;
+              const actor = context.payload.comment.user.login;
+              prNumber = String(context.payload.issue.number);
+              const perm = await permissionFor(actor);
+              authorized = perm.level === 'admin' || perm.role === 'maintain';
+              if (authorized) {
+                const { data: pr } = await github.rest.pulls.get({ owner, repo, pull_number: Number(prNumber) });
+                if (pr.state !== 'open') {
+                  authorized = false;
+                  core.info(`PR #${prNumber} is ${pr.state}; refusing to preview.`);
+                } else {
+                  headSha = pr.head.sha;
+                }
+              }
+              core.info(`/preview-docs by ${actor} (level=${perm.level}, role=${perm.role}) → authorized=${authorized}`);
+            }
+
+            core.setOutput('authorized', String(authorized));
+            core.setOutput('pr_number', prNumber);
+            core.setOutput('head_sha', headSha);
+            core.setOutput('slash_attempt', String(slashAttempt));
+
+  build:
+    needs: authorize
+    if: needs.authorize.outputs.authorized == 'true'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+        with:
+          ref: ${{ needs.authorize.outputs.head_sha }}
+          persist-credentials: false
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@fac544c07dec837d0ccb6301d7b5580bf5edae39 # v8.2.0
+        with:
+          enable-cache: true
+          version: 0.9.5
+
+      - run: uv sync --frozen --group docs
+      - run: uv run --frozen --no-sync mkdocs build
+
+      - uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: site
+          path: site/
+          retention-days: 1
+
+  deploy:
+    needs: [authorize, build]
+    if: needs.authorize.outputs.authorized == 'true'
+    runs-on: ubuntu-latest
+    permissions: {}
+    outputs:
+      deployment_url: ${{ steps.wrangler.outputs.deployment-url }}
+      alias_url: ${{ steps.wrangler.outputs.pages-deployment-alias-url }}
+    steps:
+      - uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          name: site
+          path: site
+
+      - name: Deploy to Cloudflare Pages
+        id: wrangler
+        uses: cloudflare/wrangler-action@ebbaa1584979971c8614a24965b4405ff95890e0 # v4.0.0
+        with:
+          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
+          accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
+          packageManager: npm
+          command: >-
+            pages deploy ./site
+            --project-name=${{ vars.CLOUDFLARE_PAGES_PROJECT }}
+            --branch=pr-${{ needs.authorize.outputs.pr_number }}
+            --commit-hash=${{ needs.authorize.outputs.head_sha }}
+            --commit-dirty=true
+
+  comment:
+    needs: [authorize, build, deploy]
+    if: >-
+      always() &&
+      needs.deploy.result != 'cancelled' &&
+      (needs.authorize.outputs.authorized == 'true' || needs.authorize.outputs.slash_attempt == 'true')
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - name: Post or update preview comment
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
+        env:
+          AUTHORIZED: ${{ needs.authorize.outputs.authorized }}
+          PR_NUMBER: ${{ needs.authorize.outputs.pr_number }}
+          HEAD_SHA: ${{ needs.authorize.outputs.head_sha }}
+          DEPLOY_RESULT: ${{ needs.deploy.result }}
+          DEPLOYMENT_URL: ${{ needs.deploy.outputs.deployment_url }}
+          ALIAS_URL: ${{ needs.deploy.outputs.alias_url }}
+          RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
+        with:
+          script: |
+            const { owner, repo } = context.repo;
+            const env = process.env;
+            const issue_number = Number(env.PR_NUMBER);
+            const marker = '<!-- docs-preview -->';
+
+            async function upsert(body) {
+              const comments = await github.paginate(github.rest.issues.listComments, { owner, repo, issue_number, per_page: 100 });
+              const existing = comments.find(c => c.user?.type === 'Bot' && c.body?.includes(marker));
+              if (existing) {
+                await github.rest.issues.updateComment({ owner, repo, comment_id: existing.id, body });
+              } else {
+                await github.rest.issues.createComment({ owner, repo, issue_number, body });
+              }
+            }
+
+            if (env.AUTHORIZED !== 'true') {
+              await github.rest.issues.createComment({
+                owner, repo, issue_number,
+                body: `@${context.actor} — only repository admins or maintainers can run \`/preview-docs\` (and the PR must be open).`,
+              });
+              return;
+            }
+
+            if (env.DEPLOY_RESULT !== 'success') {
+              await upsert(
+                `${marker}\n### 📚 Documentation preview\n\n` +
+                `❌ Preview build **failed** for \`${env.HEAD_SHA.slice(0, 7)}\` — [workflow logs](${env.RUN_URL}).`
+              );
+              return;
+            }
+
+            const previewUrl = env.ALIAS_URL || env.DEPLOYMENT_URL;
+            const ts = new Date().toISOString().replace('T', ' ').replace(/\.\d+Z$/, ' UTC');
+            await upsert(
+              `${marker}\n### 📚 Documentation preview\n\n` +
+              `| | |\n|---|---|\n` +
+              `| **Preview** | ${previewUrl} |\n` +
+              `| **Deployment** | ${env.DEPLOYMENT_URL} |\n` +
+              `| **Commit** | \`${env.HEAD_SHA.slice(0, 7)}\` |\n` +
+              `| **Triggered by** | @${context.actor} |\n` +
+              `| **Updated** | ${ts} |\n`
+            );

.github/zizmor.yml

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+rules:
+  dangerous-triggers:
+    ignore:
+      # Both preview workflows use pull_request_target so secrets are available
+      # for fork PRs. docs-preview.yml gates PR-code execution behind an
+      # admin/maintainer permission check and isolates the build (which runs
+      # PR Python via mkdocstrings) from Cloudflare secrets via an artifact
+      # handoff. docs-preview-cleanup.yml never checks out PR code at all.
+      - docs-preview.yml
+      - docs-preview-cleanup.yml