feat: Windows portability - path separators, LF line endings, UTF-8 decoding and output, msvcrt lock fallback (#152)

Files changed:
- .gitattributes
- CHANGES.md
- VERSION
- raw/CONTRACT.md
- tools/README.md
- tools/chemenu/commands/_util.py
- tools/chemenu/commands/dist_cmd.py
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/doctor.py
- tools/chemenu/commands/eval_cmd.py
- tools/chemenu/commands/git_publish.py
- tools/chemenu/commands/index_build.py
- tools/chemenu/commands/lint.py
- tools/chemenu/commands/log_append.py
- tools/chemenu/commands/migrate_cmd.py
- tools/chemenu/commands/provenance_cmd.py
- tools/chemenu/commands/raw_cmd.py
- tools/chemenu/commands/run_budget.py
- tools/chemenu/commands/upstream_cmd.py
- tools/chemenu/commands/version_cmd.py
- tools/chemenu/commands/work_cmd.py
- tools/chemenu/config.py
- tools/chemenu/corpus_cache.py
- tools/chemenu/filelock.py
- tools/chemenu/frontmatter_io.py
- tools/chemenu/kb_scan.py
- tools/chemenu/kb_state.py
- tools/chemenu/lint_core.py
- tools/chemenu/prerequisites.py
- tools/chemenu/provenance.py
- tools/chemenu/search/base.py
- tools/chemenu/search/ripgrep.py
- tools/chemenu/telemetry/writer.py
- tools/chemenu/tests/test_dist_cmd.py
- tools/chemenu/tests/test_portability.py
- tools/chemenu/tests/test_search.py
- tools/chemenu/tests/test_trace_ingest.py
- tools/chemenu/type_resolver.py
- tools/chemenu/upload.py
- tools/chemenu/version.py
- tools/run_wikitool.py
- tools/trace_ingest.py

tools/chemenu/commands/raw_cmd.py

@@ -122,10 +122,10 @@ def _validate_under_incoming(path: Path, incoming: Path) -> None:
             "from there. See raw/CONTRACT.md."
         )
     if len(rel.parts) < 1:
-        fail(f"incoming/{rel} names no file.")
+        fail(f"incoming/{rel.as_posix()} names no file.")
     if len(rel.parts) > 2:
         fail(
-            f"incoming/{rel} is nested more than one level below incoming/ - place it "
+            f"incoming/{rel.as_posix()} is nested more than one level below incoming/ - place it "
             "directly in incoming/, or in at most one subdirectory of it (the "
             "subdirectory itself is ignored, see raw/CONTRACT.md)."
         )