[WIP] docs: clear docs/ for the Mintlify docs source

[ShawnChen-Sirius]

Why

Following the docs-platform alignment, chdb-io/chdb/docs will become the aggregation source for the official chDB documentation (synced into the main ClickHouse docs build — the same model clickhouse-connect adopted in ClickHouse/clickhouse-connect#778). This PR clears the directory, stages the published docs tree in it, and wires up tooling and CI ahead of the 7/17 platform cutover — without switching the source of truth yet (see the staging notice in docs/README.md; content edits keep flowing through the live pipeline until the cutover stabilizes).

What

1. Three-way split of the old docs/ (references updated):

• Sphinx site → sphinx/ (.readthedocs.yml, Makefile, ruff exclude, CONTRIBUTING follow)
• Engineering references → dev-docs/ (README/CONTRIBUTING/llms.txt links and the llms-full generator follow)
• docs/_static/ stays put: its images are pinned by absolute raw URLs from the org profile, every published PyPI release page, and the example notebooks — frozen public URLs.

2. ReadTheDocs retirement banner — canonical docs are clickhouse.com/docs/chdb; RTD stops updating September 17, 2026.

3. Staged docs snapshot — the docs/products/chdb slice of the aggregated docs in ClickHouse/ClickHouse (44 Mintlify .mdx pages + navigation.json, snapshot of 2026-07-08) imported into docs/, with a README marking it a staging copy, not the source of truth.

4. llms-full generator: dual source — --docs-source local builds from the staged tree (aggregator-internal /products/chdb/… links resolved to published slugs); default stays remote until the source-of-truth switch. Both modes emit identical URLs for all 44 pages. Also fixes a real bug in the shipped llms-full.txt: Python/Go import lines inside code examples were being stripped by the MDX-import regex (20 import chdb lines were missing); regenerated.

5. Docs verification CI — clickhouse-connect's docs_verify.yml adapted: the aggregator's products/chdb slice is replaced with this repo's staged pages and the scoped Mintlify checks run on every PR touching docs/. README/_static are filtered out of the staged slice — the same whitelist the future sync workflow will use.

6. Content diff verdict (dev-docs vs docs pages): every overlapping dev-docs file contains substantial content the docs pages lack (22–69 headings each; PANDAS_COMPATIBILITY and FUNCTIONS are ~3× the size of their counterparts). Nothing is deleted; they stay in dev-docs/ as source material for enriching the docs pages later.

After the cutover stabilizes (not in this PR)

Final re-sync of the snapshot → flip the generator default to local → replace the staging notice with contributor instructions → sync workflow + pre-merge preview with the docs team. At that point docs/ becomes the single source of truth.

🤖 Generated with Claude Code

Note

Move Sphinx docs to sphinx/ and populate docs/ with Mintlify source

• Relocates all existing Sphinx documentation files from docs/ to sphinx/ so that docs/ can be used exclusively for the new Mintlify-based docs source.
• Adds a large set of new Mintlify .mdx pages under docs/ covering installation guides (Python, Node.js, Go, Rust, Bun, C/C++), DataStore reference, configuration, debugging, guides, and API reference.
• Moves internal developer documents (architecture, migration guides, etc.) from docs/ to dev-docs/ and updates all cross-references in README.md, CONTRIBUTING.md, llms.txt, and llms-full.txt.
• Updates build tooling: Makefile, .readthedocs.yml, pyproject.toml, and .gitignore now point to sphinx/ instead of docs/.
• Adds a CI workflow (.github/workflows/docs_verify.yml) that runs Mintlify docs validation against the docs/ tree on PRs and pushes to main.
• Behavioral Change: make docs and make docs-md now build from sphinx/; Read the Docs builds from sphinx/conf.py and sphinx/requirements.txt.

^{Macroscope summarized f9662ac.}