[raminqaf]

What is the purpose of the change

Step 2 of FLINK-23804: every function of five categories gets a page of its own, generated from YAML. A page has the SQL, Java and Python syntax, the arguments, what it returns and when it returns NULL, usage notes, and examples. Each function was rechecked against its implementation, and every example result comes from running its SQL. The recheck changed what the docs say, for example:

Function	Old docs	Master
REGEXP_REPLACE	Says nothing about the replacement	$1 is inserted as written. The replacement can't refer to groups.
REGEXP_EXTRACT_ALL	extractIndex defaults to 1	So a regex without groups returns NULL unless you pass 0
RANK	"one plus the number of rows preceding or equal to the current row"	One plus the rows before it. Peers aren't counted.
TRY_CAST	COALESCE(TRY_CAST('non-number' AS INT), 0) "returns 0 of type INT"	The type is INT NOT NULL
LEAD	No mention of streaming	Not supported in streaming mode

Brief change log

• Bump Hugo from 0.124.1 to 0.126.3. The pages come from a content adapter, which needs Hugo 0.126. The docs CI script passes --logLevel info instead of -v, which 0.126.3 logs as a deprecation error.
• Generate one page per data/functions/<category>/<name>.yml, in English and Chinese. A page starts with its category, a one-line summary and related functions, followed by the same sections: syntax, arguments, returns, usage notes and examples. A render hook for SQL code blocks highlights the page's function in its syntax and examples.
• In the category tables, a converted row shows the function's name instead of its signature, links to its page and shows the page's summary. The two CASE rows show once, and the rows are in alphabetical order, as in the sidebar. The A-Z page links converted rows to their page, and a category in the sidebar expands to its function pages.
• Use the Flink colors for code blocks and the sidebar. Keywords and SQL types are bold purple, strings dark orange and numbers black. On a function page, the page's function is bold dark red. The SQL render hook gives every SQL type name the same class, because the highlighter tags INT, TIMESTAMP and STRING in three different ways. The colors apply to every code block on the site.
• Add 33 pages: Regular Expressions 7, Cast 2, Conditional 7, Window 9, Utility 8. Every row of these categories now points at a page.
• Chinese pages show the English sections. Where a row had a Chinese description, its first sentence becomes the summary.
• Two Table API-only rows lose their Scala-only form: BOOLEAN.? folds into the IF row as BOOLEAN.then, and NUMERIC.rows becomes rowInterval(LONG).
• Add a guide for function pages to docs/README.md, including what a page leaves out, and point AGENTS.md step 8 at it.

Verifying this change

This change is documentation only.

• Every SQL example ran in batch and streaming mode on master with a local runner, which isn't part of this PR. The results on the pages are pasted from those runs.
• A second review per category checked each statement against the type strategies, the runtime code and the tests.
• Hugo 0.126.3 builds both languages without warnings. A link check finds no new broken internal links. The A-Z page still lists 241 functions in English and 238 in Chinese, as on master, and 15 Table API-only entries instead of 16.
• Every commit builds on its own.

The recheck found bugs in the code, which this PR doesn't fix. The pages describe the intended behavior, and I'll file the bugs separately.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

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Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

Generated-by: Claude Code 2.1.322 (Claude Opus 5.5)

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CI report:

• 4ed3cf9 Azure: SUCCESS

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