Add context to the project wiki from free-form text.

The user provided this context: $ARGUMENTS

1. Read `.wiki/_index.md` to understand existing domains
2. Determine which domain this context belongs to (ask if unclear)
3. Find the appropriate note in `.wiki/domains/` to update
4. Add the information in the right section with tag `[confirmed]` (since it comes from a human)
5. If this creates a new sub-topic, create a new note file
6. Update cross-references if this info relates to multiple domains
7. Update `.wiki/_index.md` if needed
8. Update `.wiki/_graph.md` if dependencies changed
