docs: llms-full.txt link integrity, MCP entry, and package layering

[ShawnChen-Sirius]

Follow-up to #599 (these two commits were pushed after it merged, so they land here).

llms-full.txt: every link is now absolute and alive

A full sweep of all 132 unique link targets found four kinds of broken links, all fixed in the generator:

• Site-absolute doc paths (/interfaces/formats) now carry the clickhouse.com/docs prefix.
• File-relative links (guides/querying-pandas.md) resolve through a source-path → published-slug map, because filenames and slugs diverge (that file publishes at /chdb/guides/pandas).
• Repo-relative links/images in ARCHITECTURE.md and the binding READMEs point at github.com blob / raw URLs.
• YouTube iframes become plain [Watch the video](watch URL) links; dangling <Image> tags (their MDX imports are stripped) are removed; file:/data: connection-string examples are left untouched.

Two targets were verified genuinely dead and are unwrapped to plain text via a DEAD_LINK_PREFIXES list: the JeffSackmann/tennis_atp dataset repo (404) and jupysql.ploomber.io (domain no longer resolves). The six 403 targets (npmjs, crates.io, clickpy, badge.fury.io) are bot walls — packages verified alive via the npm registry and crates.io APIs.

Result: 130 unique links in the regenerated file, zero dead.

Known upstream issue, out of scope: the JupySQL guide's code sample still downloads from the removed tennis_atp repo, so that tutorial is broken in clickhouse-docs itself.

llms.txt: two additions

• MCP entry: chDB is served through the official mcp-clickhouse server — pip install 'mcp-clickhouse[chdb]', CHDB_ENABLED=true, agents get a run_chdb_select_query tool.
• Package layering note in the header: chdb-core builds the libchdb engine binaries; chdb (Python) and the node/bun/go/rust packages are thin bindings over the same C ABI — plus routing guidance for where issues belong.

CI: dead-link gate now covers both files

The link check walks llms.txt and llms-full.txt (markdown targets plus **URL:** provenance lines), and treats unreachable-after-retries (000) as dead — a vanished domain never returns 404. 403/429 stay warning-only.

🤖 Generated with Claude Code

Note

Fix link integrity and add MCP entry in llms.txt and llms-full.txt

• Updates scripts/generate_llms_full.py to rewrite relative docs links to absolute https://clickhouse.com/docs/... URLs, convert iframe embeds to YouTube watch links, remove <Image /> tags, and unwrap known-dead external links to plain text.
• Adds a two-pass slug map in the generator so intra-doc links are resolved before emission; GitHub-sourced relative links are rewritten to github.com blob or raw.githubusercontent.com URLs depending on whether they point to images.
• Updates .github/workflows/llms-txt-check.yml to validate links in both llms.txt and llms-full.txt, treat HTTP 000 as dead alongside 404/410, and log 403/429 as warnings.
• Adds a 'How the packages relate' bullet (chdb-core vs language bindings) and an MCP server entry to llms.txt.

^{Macroscope summarized 3fcefde.}