Stage 14: solver & dictionary split — consume published module + DAWG artifact (TODO-1/TODO-2)

- backend/go.mod pins gitea.iliadenisov.ru/developer/scrabble-solver v1.0.0; the engine's
  imports use the published module path; go.work drops the solver replace (GOPRIVATE fetches
  it directly from Gitea). The solver's wordlist/dictdawg are now public packages.
- CI (go-unit, integration): drop the solver sibling-clone, set GOPRIVATE, and download the
  dictionary DAWG release artifact (scrabble-dawg-<DICT_VERSION>.tar.gz from the new
  scrabble-dictionary repo) for BACKEND_DICT_DIR.
- Docs: ARCHITECTURE §5/§11/§13/§14 + backend/README updated to the published-module +
  release-artifact model. PLAN.md re-scoped Stage 14 to the split and added Stages 15 (deploy
  infra & test contour), 16 (prod contour), 17 (dual Telegram bots); TODO-1/TODO-2 marked done.

.gitea/workflows/integration.yaml

@@ -35,16 +35,25 @@ jobs:
       # Ryuk (testcontainers' reaper) does not start cleanly on every runner;
       # the suite's TestMain terminates its own container, so disable it.
       TESTCONTAINERS_RYUK_DISABLED: "true"
+      # The engine consumes the published scrabble-solver module from this Gitea
+      # (GOPRIVATE -> direct fetch, skipping the public proxy/checksum DB);
+      # DICT_VERSION selects the dictionary DAWG release the engine tests load.
+      GOPRIVATE: gitea.iliadenisov.ru/*
+      DICT_VERSION: v1.0.0
     steps:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Fetch scrabble-solver (sibling)
-        # The backend now imports the engine package, which consumes
-        # scrabble-solver in-process; go.work points its bare module path at this
-        # sibling checkout. The repository is public, so the clone needs no
-        # credentials. It tracks master HEAD (see PLAN.md TODO-1).
-        run: git clone --depth 1 https://gitea.iliadenisov.ru/developer/scrabble-solver.git "${GITHUB_WORKSPACE}/../scrabble-solver"
+      - name: Fetch dictionary DAWGs
+        # The DAWGs moved to the scrabble-dictionary repo (the solver is now a
+        # versioned module pinned in backend/go.mod, fetched via GOPRIVATE — no
+        # sibling clone). They ship as a release artifact; the engine's untagged
+        # tests (compiled here too) load them.
+        run: |
+          mkdir -p "${GITHUB_WORKSPACE}/dawg"
+          curl -fsSL -o /tmp/dawg.tar.gz "https://gitea.iliadenisov.ru/developer/scrabble-dictionary/releases/download/${DICT_VERSION}/scrabble-dawg-${DICT_VERSION}.tar.gz"
+          tar xzf /tmp/dawg.tar.gz -C "${GITHUB_WORKSPACE}/dawg"
+          ls -la "${GITHUB_WORKSPACE}/dawg"
 
       - name: Set up Go
         uses: actions/setup-go@v5
@@ -56,7 +65,7 @@ jobs:
         # -count=1 disables the test cache; -p=1 -parallel=1 keeps the
         # container-backed tests serial; the 15-minute timeout bounds a stuck
         # container pull. The engine package's (untagged) tests also compile and
-        # run here, so BACKEND_DICT_DIR points them at the committed DAWGs.
+        # run here, so BACKEND_DICT_DIR points them at the DAWGs from the release.
         env:
-          BACKEND_DICT_DIR: ${{ github.workspace }}/../scrabble-solver/dawg
+          BACKEND_DICT_DIR: ${{ github.workspace }}/dawg
         run: go test -tags=integration -count=1 -p=1 -parallel=1 -timeout=15m ./backend/...