chore: initial bootstrap — 5 reusable workflows + scaffolding

Public-readable Tier-1 exception (alongside sporel-meta) for the
practical reason that community pipelines need to call into these
workflows without per-repo deploy-token setup.

5 reusable workflows moved from sporel-meta/.gitea/workflows/ to here
(Plan-B.1: privacy-fix for sporel-meta which stays private with the
proprietary design docs).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/reusable-docs.yml

@@ -0,0 +1,43 @@
+# Reusable workflow: Meta / Docs / Tool (Cat 5 per ADR-0025)
+# Markdown lint + internal link check
+name: Docs CI
+
+on:
+  workflow_call:
+    inputs:
+      lint_paths:
+        description: "Glob of paths to lint"
+        type: string
+        default: "**/*.md"
+      ignore_paths:
+        description: "Glob of paths to skip (e.g. archive)"
+        type: string
+        default: "**/archive/**"
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Node + markdownlint-cli2
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y nodejs npm
+          sudo npm install -g markdownlint-cli2
+
+      - name: Run markdownlint
+        run: |
+          markdownlint-cli2 "${{ inputs.lint_paths }}" "!${{ inputs.ignore_paths }}" || \
+            (echo "::warning::markdown lint warnings (non-blocking)" && true)
+
+      - name: Internal link check (lychee)
+        uses: lycheeverse/lychee-action@v2
+        with:
+          args: --offline --no-progress --include-fragments "**/*.md" --exclude-path "**/archive/**"
+          fail: true
+
+      - name: README presence (root)
+        run: |
+          test -s README.md || (echo "::warning::no README.md at repo root" && true)