docs: make the training exercise safe to fork

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  exercise-checks:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+          cache: npm
+      - run: npm ci --ignore-scripts --no-audit --no-fund
+      - run: npm run typecheck
+      - name: Verify tests or expected starter state
+        shell: bash
+        run: |
+          set +e
+          npm test -- --runInBand
+          result=$?
+          set -e
+          if [ "$result" -eq 0 ]; then
+            exit 0
+          fi
+          if grep -q "Not implemented" engine.ts; then
+            echo "Starter exercise intentionally retains unimplemented methods."
+            exit 0
+          fi
+          echo "Tests failed after the starter placeholders were removed."
+          exit "$result"

FAN_FORK_GUIDE.md

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+# Fan Fork Guide
+
+This repository may be forked for self-directed learning and fan experimentation.
+
+## Required boundaries
+
+- Keep the MIT notice with software copied from this repository.
+- Attribute Loptr Lab and apply CC BY-NC-SA 4.0 to adapted curriculum,
+  instructions, narrative, or scoring materials.
+- Give the fork distinct branding and state: "Unofficial fan fork; not evaluated
+  or endorsed by Loptr Lab."
+- Do not claim that completing a fork provides employment consideration,
+  academic credit, certification, workforce funding, or an official score.
+- Do not submit personal, disability, vocational-rehabilitation, education, or
+  employment records through GitHub issues or pull requests.
+- Never include API keys, production credentials, private evaluation notes, or
+  identifiable participant data.
+
+## Canon boundary
+
+Ember, Tide, Root, Gale, Burning, and Steam are training abstractions. Fan
+solutions and changes remain noncanonical. The four-player rules authority is
+[Loptr-Lab/veiled-dominion-engine](https://github.com/Loptr-Lab/veiled-dominion-engine);
+Duet remains a separate experimental accessibility artifact.
+
+## Running safely
+
+Use `npm ci`, `npm run typecheck`, and `npm test`. No secret or production
+service is required. Work on a branch in your fork and preserve the mandatory
+tests if you want results comparable to the published exercise.

LICENSE-CODE.md

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+MIT License
+
+Copyright (c) 2026 Loptr Lab
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of the software and associated software documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation the
+rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is furnished
+to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.