incoming/.gitkeep als Datei- statt Verzeichnismuster trackbar (schliesst #88)

Files changed:
- .gitignore
- CHANGES.md
- README.md
- VERSION
- incoming/.gitkeep
- instructions/bootstrap.md
- raw/CONTRACT.md
- tools/CONTRACT.md
- tools/chemenu/commands/docs_verify.py

README.md

@@ -79,7 +79,7 @@ chemenu/
 ├── mcp-upload/         # QUARANTINE (optional): the MCP `submit` tool's write path, gitignored -
 │                       #   read by no command in the ordinary pipeline; a human reviews it with
 │                       #   `wikitool upload list/show/accept/reject`
-├── incoming/           # INBOX: gitignored and flat - drop a file here, `raw accept` promotes it
+├── incoming/           # INBOX: flat, content gitignored - drop a file here, `raw accept` promotes it
 ├── raw/                # INPUT: immutable, untrusted source material
 │   ├── CONTRACT.md     # Date shard, capture fields, immutability, untrusted content
 │   ├── 2026/09/        # Where `raw accept` puts a file: the month it was accepted