studio: version text in the status bar, favicon

The status bar ends with "isokit <engine version>"; the web build adds
the commit (linked on Gitea), its date as a tooltip and a "+" when built
from a tree with uncommitted changes (build_web.py writes a
<meta name="isokit-build"> from GITHUB_SHA or git). /api/meta now carries
"engine". studio/favicon.svg (isometric cube in the accent green) is
served by `isokit studio` (also on /view) and copied into the web build.
check_web.py and check_studio.py check both.

tools/build_web.py

@@ -81,6 +81,24 @@ def demo_files():
     return out
 
 
+def build_info():
+    """'<commit> <commit date> [dirty]' for the version text in the Studio's
+    status bar; GITHUB_SHA (CI) wins over git. Empty when git is missing."""
+    def git(*args):
+        r = subprocess.run(["git", *args], capture_output=True, text=True, cwd=ROOT)
+        return r.stdout.strip() if r.returncode == 0 else ""
+    try:
+        sha = os.environ.get("GITHUB_SHA") or git("rev-parse", "HEAD")
+        if not sha:
+            return ""
+        parts = [sha, git("log", "-1", "--format=%cs", sha) or "-"]
+        if git("status", "--porcelain", "--untracked-files=no"):
+            parts.append("dirty")
+        return " ".join(parts)
+    except OSError:
+        return ""
+
+
 def replace_once(s, old, new):
     n = s.count(old)
     assert n == 1, f"studio/index.html: expected {old!r} once, found {n}"
@@ -116,7 +134,7 @@ def main():
         print("  (wasm-opt not found: the .wasm stays unoptimised by binaryen, about 15% larger)")
 
     for src, dst in [("viewer/isokit-view.js", "viewer"), ("viewer/isokit-view.css", "viewer"),
-                     ("studio/studio.js", "studio"), ("studio/studio.css", "studio"),
+                     ("studio/studio.js", "studio"), ("studio/studio.css", "studio"), ("studio/favicon.svg", "studio"),
                      ("web/web.js", "web"), ("web/web.css", "web")]:
         (out / "assets" / dst).mkdir(parents=True, exist_ok=True)
         shutil.copy2(ROOT / src, out / "assets" / dst / Path(src).name)
@@ -129,8 +147,11 @@ def main():
     v = "v=" + h.hexdigest()[:10]
 
     html = (ROOT / "studio" / "index.html").read_text(encoding="utf-8")
+    build = build_info()
     html = replace_once(html, '<title>isokit Studio</title>',
-                        '<title>isokit Studio</title>\n<meta name="description" content="isokit Studio: edit isometric site plans in the browser.">')
+                        '<title>isokit Studio</title>\n<meta name="description" content="isokit Studio: edit isometric site plans in the browser.">'
+                        + (f'\n<meta name="isokit-build" content="{build}">' if build else ""))
+    html = replace_once(html, 'href="/assets/studio/favicon.svg"', f'href="assets/studio/favicon.svg?{v}"')
     html = replace_once(html, 'href="/assets/viewer/isokit-view.css"', f'href="assets/viewer/isokit-view.css?{v}"')
     html = replace_once(html, '<link rel="stylesheet" href="/assets/theme.css">', '<style id="iso-theme"></style>')
     html = replace_once(html, '<link rel="stylesheet" href="/assets/studio/studio.css">',
@@ -148,7 +169,7 @@ def main():
         if p.is_file():
             total += p.stat().st_size
             print(f"  {p.relative_to(out).as_posix():40} {p.stat().st_size / 1024:8.1f} kB")
-    print(f"{out} ({total / 1024 / 1024:.1f} MB, {v})")
+    print(f"{out} ({total / 1024 / 1024:.1f} MB, {v}, build {build or 'unknown'})")
 
 
 if __name__ == "__main__":