[doc](sql-functions) numbered-example authoring format — array-filter.md as demo

[boluor]

Summary

Demo PR proposing a small authoring convention for sql-manual/sql-functions/ doc pages, applied here to array-filter.md (EN + ZH) as a concrete example. Looking for maintainer feedback on the shape before scaling to other pages.

The convention in one paragraph

Inside ## Examples, each runnable example becomes a numbered pair of fenced blocks:

```sql {example="N"}      ← SQL to execute (copy button, runnable)
```result {example="N"}   ← expected output (no copy)
```error {example="N"}    ← expected error (no copy)

One-time fixture data goes in ```sql {setup}. The ## Syntax block stays unchanged. EN and ZH share the same example="N" numbers, so cross-language drift becomes mechanically detectable.

Why

1. Machine-verifiable. A doc-verify tool can match every sql {example="N"} to its result|error block by ID — zero heuristic guessing about where SQL ends and output begins.
2. EN/ZH consistency. Same example numbers across languages → missing or drifted examples are detectable by tooling, not by manual review.
3. UX. Readers copy SQL safely; expected output stays visually distinct and is not mis-copied as input.
4. Backward compatible. Pages that don't use the convention keep working exactly as today. It's opt-in per page.

What's in this PR

Just array-filter.md, both languages:

• versioned_docs/version-4.x/sql-manual/sql-functions/scalar-functions/array-functions/array-filter.md
• i18n/zh-CN/docusaurus-plugin-content-docs/version-4.x/sql-manual/sql-functions/scalar-functions/array-functions/array-filter.md

Before / after (one example)

Before:

Using lambda expression to filter elements in double_array greater than or equal to 3:
```sql
SELECT array_filter(x -> x >= 3, double_array) FROM array_filter_test WHERE id = 1;
+------------------------------------------+
| array_filter(x -> x >= 3, double_array)  |
+------------------------------------------+
| [3.3, 4.4, 5.5]                          |
+------------------------------------------+
```

After:

**Example 1** — Lambda over a DOUBLE array column: keep elements `>= 3`.

```sql {example="1"}
SELECT array_filter(x -> x >= 3, double_array) FROM array_filter_test WHERE id = 1;
```

```result {example="1"}
+------------------------------------------+
| array_filter(x -> x >= 3, double_array)  |
+------------------------------------------+
| [3.3, 4.4, 5.5]                          |
+------------------------------------------+
```

Bundled fix

The original EN page had a code block at line ~164 with only the result table (the SELECT statement was missing). Reconstructed the SELECT from the result column header — it is now Example 9.

Verification

Ran every example on a single-node Apache Doris 4.1.1 cluster:

• EN: 20 pass / 0 fail / 1 not_checked (Syntax illustrative block)
• ZH: 20 pass / 0 fail / 1 not_checked
• All 4 error examples carry kind=error expected output and match the actual errCode = …, detailMessage = … from Doris, after stripping environment-specific IP prefixes.

Rendering

Without any theme changes, docusaurus renders:

• sql fences with syntax highlight + copy button (default behavior, unchanged)
• result and error fences as plain code blocks (Prism doesn't know these languages, so no highlight; copy button still present by default)

The convention's full UX (red-styled error block, no copy on result/error) needs a small theme override, which would be a separate follow-up PR. This PR does not require any theme change — the markdown is valid and renders correctly today.

Asking for

• Is the convention shape ({example="N"}, three fence types) OK?
• Where should the full authoring spec live? Suggestions: .docs-governance/ or doc-tools/. A separate spec-doc PR can follow.
• If approved, follow-ups will convert other array-* function pages in the same style.

Co-authored-by: doris-verify #3781