[YQ-4843] Watermarks: docs

[APozdniakov]

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✅ Documentation build

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Warnings (8)

⚠️ ru/concepts/streaming_query/formats.md: 60: MD031 / blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]

⚠️ ru/concepts/streaming_query/index.md: 26: MD001 / heading-increment Heading levels should only increment by one level at a time [Expected: h2; Actual: h3]

⚠️ ru/public-materials/videos/2025.md: 25: MD009 / no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]

⚠️ ru/public-materials/videos/2025.md: 39: MD009 / no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]

⚠️ ru/public-materials/videos/2025.md: 45: MD009 / no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]

⚠️ ru/public-materials/videos/2025.md: 59: MD009 / no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]

⚠️ ru/public-materials/videos/2025.md: 7: MD009 / no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]

⚠️ ru/public-materials/videos/2025.md: 9: MD009 / no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]