Add query-first wiki MCP server

[EthanThatOneKid]

Summary

• add a read-only wiki mcp stdio server backed by the existing Wiki graph query path
• expose query_sparql, describe_wiki, and lightweight wiki:// resources
• include observed class/predicate vocabulary in describe_wiki so agents can write grounded SPARQL
• add a minimal TypeScript wiki.mcp() spawn helper and docs

Addressing m13v comment

Credit to @m13v for calling out the real adoption risk in the issue thread:

the read-only, query-first scope is the right call. the thing that decides whether agents actually use this is describe_wiki, not query_sparql. the recurring failure mode with SPARQL over MCP is the model inventing a predicate that isn't in the graph, getting an empty result set, and reading it as "no data" rather than "bad query". namespaces alone don't prevent that, a handful of real class and predicate names would. so "should describe_wiki stay purely factual" is quietly the load-bearing open question in this issue, not the transport one.

This PR attacks that failure mode by making describe_wiki more than config plus namespaces while still keeping it factual/read-only:

• describe_wiki includes an observed vocabulary block from the current graph.
• Classes are counted from real rdf:type triples.
• Predicates are counted from actual graph triples.
• Entries include full iri, compact curie when namespace bindings support it, and usage count.
• The vocabulary is generated from the same inferred graph used by default query_sparql, so it reflects what agents actually query.
• The docs call this out explicitly as the load-bearing context that prevents invented predicates from being misread as missing data.

That keeps the MCP surface query-first without leaving agents to guess the graph schema from namespaces alone.

Verification

• uv run ruff check .
• uv run pytest
• npm run test:npm
• uv run wiki -c docs/wiki.yml fmt --check docs/wiki/Wiki_Subcommand_mcp.md docs/wiki/Wiki_CLI.md
• uv run wiki -c docs/wiki.yml lint --strict
• uv run wiki -c docs/wiki.yml check --strict
• uv run wiki -c docs/wiki.yml render --check