feat(api): /VERSION single source read at startup + GET /version

VERSION

@@ -0,0 +1 @@
+0.01-alpha

api/app/main.py

@@ -17,8 +17,9 @@ from .canon_log import validate_canon_log
 from .narrate import run as narrate_run
 from .npc import UnknownNpc, run as npc_run
 from .ollama_client import ModelError
+from .version import VERSION
 
-app = FastAPI(title="coc-rpg proxy", version="0.0.1")
+app = FastAPI(title="coc-rpg proxy", version=VERSION)
 
 
 @app.exception_handler(RequestValidationError)
@@ -65,6 +66,11 @@ def health() -> dict:
     return {"status": "ok"}
 
 
+@app.get("/version")
+def version() -> dict:
+    return {"version": VERSION}
+
+
 # ── Role endpoints (charter §4) ──────────────────────────────────────────────
 # The client knows these paths and nothing about which model or prompt serves
 # them. Bodies are validated against the canon log contract. /dm/narrate is

api/app/version.py

@@ -0,0 +1,33 @@
+"""Single source of truth for the app version (charter §4: client and API share
+one version). Reads the repo-root /VERSION file — the ONLY place a human edits the
+version. Mirrors canon_log._schema_dir's env-override + walk-up so it resolves in
+a local checkout and (once /VERSION is bundled) an image alike.
+"""
+import os
+from functools import lru_cache
+from pathlib import Path
+
+LAST_RESORT = "0.0.0-dev"
+
+
+def _version_file() -> Path | None:
+    env = os.environ.get("COC_VERSION_FILE")
+    if env:
+        return Path(env)
+    here = Path(__file__).resolve()
+    for parent in here.parents:
+        candidate = parent / "VERSION"
+        if candidate.is_file():
+            return candidate
+    return None
+
+
+@lru_cache(maxsize=1)
+def get_version() -> str:
+    path = _version_file()
+    if path is None or not path.is_file():
+        return LAST_RESORT
+    return path.read_text(encoding="utf-8").strip() or LAST_RESORT
+
+
+VERSION = get_version()

api/tests/test_version.py

@@ -0,0 +1,22 @@
+from pathlib import Path
+
+from fastapi.testclient import TestClient
+
+from app.main import app
+from app.version import VERSION, get_version
+
+client = TestClient(app)
+ROOT_VERSION = Path(__file__).resolve().parents[2] / "VERSION"
+
+
+def test_get_version_matches_file():
+    assert ROOT_VERSION.is_file()
+    assert get_version() == ROOT_VERSION.read_text(encoding="utf-8").strip()
+
+
+def test_app_version_matches():
+    assert app.version == VERSION == get_version()
+
+
+def test_version_endpoint():
+    assert client.get("/version").json() == {"version": VERSION}