Update DuckDB docs r.e. using native File System

[gatesn]

We should update the DuckDB documentation to describe how the Vortex extension makes use of DuckDB's own file system, meaning all configs (e.g. S3 creds) should defer to DuckDb's configuration docs, e.g. https://duckdb.org/docs/stable/core_extensions/httpfs/s3api

[gatesn]

@claude take this

[claude]

Claude finished @gatesn's task in 1m 24s —— View job

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Working on Issue #6548

• Gather context and understand request
• Find existing DuckDB documentation
• Update user-guide docs to describe native file system usage
• Update developer-guide docs to describe native file system usage
• Push changes — push blocked (GitHub Actions bot lacks write access to this repo)

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Summary

I've updated both DuckDB documentation files to describe how the Vortex extension uses DuckDB's own file system.

Changes made:

docs/user-guide/duckdb.md — Added a new "Cloud Storage and Remote Files" section that:

• Explains that Vortex routes all I/O through DuckDB's file system layer
• Shows examples of reading from and writing to S3 (s3:// URIs)
• Defers credential/config setup to DuckDB's own docs with links to:
  • S3 API (httpfs)
  • Azure extension
  • HTTP(S) / httpfs
• Includes a note with a concrete S3 setup example using SET s3_region / SET s3_access_key_id

docs/developer-guide/integrations/duckdb.md — Added a new "File System" section (placed before "Registration") that:

• Names the specific Rust types (DuckDbFsReader, DuckDbFsWriter) and C bridge functions (duckdb_vx_fs_open, duckdb_vx_fs_read, duckdb_vx_fs_glob, etc.)
• Explains that inheriting DuckDB's file system plugins (httpfs, Azure) requires no Vortex-specific config
• Links back to the user guide for end-user examples

The changes are committed locally as cf448f5 on branch claude/issue-6548-20260217-0948, but I'm unable to push due to repository permissions for the Actions bot. You can apply the patch manually or grant push access to the bot.