docs: Document DAX cross-view filtering

[MazterQyou]

Check List

• Tests have been run in packages where changes have been made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

Description of Changes Made

This PR adds documentation on DAX cross-view filtering.

[claude]

Claude finished @MazterQyou's task in 1m 14s —— View job

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Review of PR #10891 — DAX Cross-View Filtering Docs

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Overall this is a well-written documentation addition. The content is clear, the examples are helpful, and it follows the docs site conventions (components like <EnvVar>, <WarningBox>, <Btn>, reference-style links at the bottom). A few minor items below.

Nit: Repetitive phrasing

cross-view-filter.mdx:13-15 — The phrase "single-perspective mode in the DAX API" appears twice in consecutive sentences:

To use cross-view filters such as slicers, you must enable single-perspective mode in the DAX API. To enable single-perspective mode in the DAX API, set the CUBEJS_DAX_SINGLE_PERSPECTIVE environment variable to true.

Consider tightening to something like:

To use cross-view filters such as slicers, you must enable single-perspective mode in the DAX API by setting the CUBEJS_DAX_SINGLE_PERSPECTIVE environment variable to true.

Nit: Missing newline at end of _meta.js

The diff shows \ No newline at end of file on _meta.js. This was pre-existing, but since the file is being modified anyway, it would be nice to add a trailing newline.

Observation: Pre-existing duplicate Power BI refs in index.mdx

Not introduced by this PR, but index.mdx defines both [ref-powerbi] (line 83) and [ref-power-bi] (line 92) pointing to the same URL. Not a blocker, just noting it for a potential future cleanup.

Looks good

• Navigation entry in _meta.js is correctly ordered before "Reference"
• The summary section added to index.mdx is well-placed under "Data modeling" and provides a good lead-in to the dedicated page
• Reference links all resolve to valid paths
• Custom components (<EnvVar>, <WarningBox>, <Btn>) are used correctly per the docs style guide
• The DirectQuery best-practice guidance (hub-and-spoke relationship pattern) is a nice practical touch

LGTM with the minor nits above.