fix(web): handle non-UTF8 Windows console encodings in _build_web_ui

Codex review pointed out that even with the sync-assets fix applied,
_build_web_ui still crashes on a stock Windows console before reaching
npm: Python stdout defaults to cp1252 (or similar) and raises
UnicodeEncodeError when print() hits the arrow/check glyphs used for
status messages (→, ✗, ⚠, ✓). Reproduced locally in PowerShell:

    $ PYTHONIOENCODING=cp1252 python -c "from hermes_cli.main import _build_web_ui; _build_web_ui(Path('web'), fatal=True)"
    UnicodeEncodeError: 'charmap' codec can't encode character '\u2192' ...

The previous PR body claimed "end-to-end verified on Windows 11", but
that was under the venv's default (utf-8) stdout. A plain `py` or
PowerShell invocation would still fail before sync-assets ever ran.

Fix: inner _say() helper that falls back to
  text.encode(sys.stdout.encoding, errors="replace")
when print() raises UnicodeEncodeError. Glyphs degrade to '?' on
ASCII / cp1252 consoles; utf-8 consoles are unaffected. Verified the
full build pipeline runs to completion with PYTHONIOENCODING=cp1252.

Scoped tightly to _build_web_ui (the function this PR already touches);
other call sites in the codebase with the same risk are out of scope.

hermes_cli/main.py

@@ -5681,13 +5681,25 @@ def _build_web_ui(web_dir: Path, *, fatal: bool = False) -> bool:
     if not _web_ui_build_needed(web_dir):
         return True
 
+    # Console-encoding-safe print: Windows consoles default to cp1252
+    # (or similar) and will raise UnicodeEncodeError on arrow / check
+    # glyphs unless PYTHONIOENCODING=utf-8 is set. Routing every print
+    # in this function through _say() with errors="replace" keeps the
+    # build path usable on a stock `py -m hermes_cli.main web` invocation.
+    def _say(text: str) -> None:
+        try:
+            print(text)
+        except UnicodeEncodeError:
+            encoding = getattr(sys.stdout, "encoding", None) or "ascii"
+            print(text.encode(encoding, errors="replace").decode(encoding, errors="replace"))
+
     npm = shutil.which("npm")
     if not npm:
         if fatal:
-            print("Web UI frontend not built and npm is not available.")
+            _say("Web UI frontend not built and npm is not available.")
-            print("Install Node.js, then run:  cd web && npm install && npm run build")
+            _say("Install Node.js, then run:  cd web && npm install && npm run build")
         return not fatal
-    print("→ Building web UI...")
+    _say("→ Building web UI...")
 
     def _relay(result: "subprocess.CompletedProcess") -> None:
         """Print captured npm output so users can see *why* a step failed.
@@ -5702,17 +5714,17 @@ def _build_web_ui(web_dir: Path, *, fatal: bool = False) -> bool:
                 continue
             text = blob.decode("utf-8", errors="replace").rstrip() if isinstance(blob, bytes) else blob.rstrip()
             if text:
-                print(text)
+                _say(text)
 
     r1 = _run_npm_install_deterministic(npm, web_dir, extra_args=("--silent",))
     if r1.returncode != 0:
-        print(
+        _say(
             f"  {'✗' if fatal else '⚠'} Web UI npm install failed"
             + ("" if fatal else " (hermes web will not be available)")
         )
         _relay(r1)
         if fatal:
-            print("  Run manually:  cd web && npm install && npm run build")
+            _say("  Run manually:  cd web && npm install && npm run build")
         return False
     # First attempt
     r2 = subprocess.run(
@@ -5747,20 +5759,20 @@ def _build_web_ui(web_dir: Path, *, fatal: bool = False) -> bool:
         # A stale UI is far better than no UI for non-interactive callers
         # (Windows Scheduled Tasks, CI) — issue #23817.
         if dist_index.exists():
-            print("  ⚠ Web UI build failed — serving stale dist as fallback")
+            _say("  ⚠ Web UI build failed — serving stale dist as fallback")
             if stderr_tail:
-                print(f"  Build error:\n  {stderr_tail}")
+                _say(f"  Build error:\n  {stderr_tail}")
             return True
 
-        print(
+        _say(
             f"  {'✗' if fatal else '⚠'} Web UI build failed"
             + ("" if fatal else " (hermes web will not be available)")
         )
         _relay(r2)
         if fatal:
-            print("  Run manually:  cd web && npm install && npm run build")
+            _say("  Run manually:  cd web && npm install && npm run build")
         return False
-    print("  ✓ Web UI built")
+    _say("  ✓ Web UI built")
     return True