feat(release): SemVer + ludicc --version, changesets, and x release

The project had no versioning discipline: 0 tags, no CHANGELOG, no way for the
compiler to report a version. Add a lightweight, native release flow.

- Versioning: SemVer, with VERSION as the single source of truth. `ludicc
  --version` (and `ludic --version`) read it at runtime — so a bump touches one
  file and never reseeds the compiler. `x version` reports it too.
- Changesets: one small Markdown file per user-facing change under changes/
  (bump level + type + summary; see changes/README.md). This replaces "remember
  to edit the changelog" with a mergeable artifact, no Node changeset tool.
- `x release [major|minor|patch] [--publish]`: fold the pending changesets into a
  new CHANGELOG.md section (grouped by type), bump VERSION, commit, and tag
  vX.Y.Z. The level defaults to the highest changeset bump. `--publish` also
  pushes and creates the Forgejo release with source + toolchain tarballs;
  tools/ci/forgejo_release.py is the small stdlib-Python HTTP glue for the
  release API (a native Http client is issue #6).

Seed the initial changesets describing the shipped surface; the first `x release`
turns them into the v0.1.0 CHANGELOG. Reseeded for the --version flag; C-free
bootstrap fixpoint holds; suites 56 / 29 / 29 on macOS, 51 / 28 (+skips) on Linux
CI, bootstrap-cfree byte-identical on both.

Part of the repository-cleanup / DX pass (with #32, #34).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/ci/forgejo_release.py

@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+"""Create a Forgejo release and attach build artifacts.
+
+    forgejo_release.py <tag> <body-file> <assets-dir>
+
+Reads the access token from $FORGEJO_TOKEN. `x release --publish` calls this
+after it has pushed the tag; it is the one piece of the release flow that speaks
+HTTP, which the Ludic task runner cannot do yet (a native Http client is issue
+#6). Python stdlib only — no third-party deps — matching the docgen tooling.
+
+Idempotent-ish: if the release for <tag> already exists it is reused, and each
+asset in <assets-dir> is uploaded (a duplicate name is skipped, not fatal).
+"""
+import json
+import os
+import sys
+import urllib.request
+import urllib.error
+
+API = "https://git.workshopsoft.io/api/v1/repos/workshopsoft/ludic"
+
+
+def token():
+    t = os.environ.get("FORGEJO_TOKEN", "").strip()
+    if not t:
+        sys.exit("forgejo_release: FORGEJO_TOKEN is not set")
+    return t
+
+
+def api(method, path, tok, data=None, headers=None, raw=False):
+    url = API + path
+    h = {"Authorization": "token " + tok}
+    body = None
+    if data is not None and not raw:
+        h["Content-Type"] = "application/json"
+        body = json.dumps(data).encode()
+    elif raw:
+        body = data
+        h.update(headers or {})
+    req = urllib.request.Request(url, data=body, headers=h, method=method)
+    with urllib.request.urlopen(req) as r:
+        return r.getcode(), json.loads(r.read().decode() or "null")
+
+
+def get_release_by_tag(tag, tok):
+    try:
+        _, rel = api("GET", "/releases/tags/" + tag, tok)
+        return rel
+    except urllib.error.HTTPError as e:
+        if e.code == 404:
+            return None
+        raise
+
+
+def main():
+    if len(sys.argv) != 4:
+        sys.exit(__doc__)
+    tag, body_file, assets_dir = sys.argv[1], sys.argv[2], sys.argv[3]
+    tok = token()
+
+    body = ""
+    if os.path.exists(body_file):
+        with open(body_file, encoding="utf-8") as fh:
+            body = fh.read()
+
+    rel = get_release_by_tag(tag, tok)
+    if rel is None:
+        _, rel = api("POST", "/releases", tok, {
+            "tag_name": tag,
+            "name": tag,
+            "body": body,
+            "draft": False,
+            "prerelease": tag.startswith("v0."),
+        })
+        print("created release", tag, "id", rel["id"])
+    else:
+        print("release", tag, "already exists (id %s); uploading assets" % rel["id"])
+
+    rid = rel["id"]
+    existing = {a["name"] for a in (rel.get("assets") or [])}
+    if os.path.isdir(assets_dir):
+        for name in sorted(os.listdir(assets_dir)):
+            if name in existing:
+                print("  skip (exists):", name)
+                continue
+            path = os.path.join(assets_dir, name)
+            if not os.path.isfile(path):
+                continue
+            with open(path, "rb") as fh:
+                blob = fh.read()
+            boundary = "----ludicrelease7f3b2a"
+            payload = (
+                ("--%s\r\n" % boundary)
+                + ('Content-Disposition: form-data; name="attachment"; filename="%s"\r\n' % name)
+                + "Content-Type: application/octet-stream\r\n\r\n"
+            ).encode() + blob + ("\r\n--%s--\r\n" % boundary).encode()
+            code, _ = api(
+                "POST", "/releases/%s/assets?name=%s" % (rid, name), tok,
+                data=payload, raw=True,
+                headers={"Content-Type": "multipart/form-data; boundary=" + boundary},
+            )
+            print("  uploaded:", name, "(HTTP %d)" % code)
+    print("done:", API + "/releases/tag/" + tag)
+
+
+if __name__ == "__main__":
+    main()