docs(plugin-transform): update how-to docs

plugin-transform-grok/src/main/resources/doc/io.kestra.plugin.transform.grok.md

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+# How to use the Transform Grok plugin
+
+Parse unstructured text — log lines, error messages, raw event data — into structured fields using Grok patterns.
+
+## Tasks
+
+`TransformValue` applies one or more Grok patterns to a single string value passed via `from` and returns the captured named fields as a map. Use it to parse a single string already in your flow's variables.
+
+`TransformItems` reads a file from Kestra internal storage (passed as a `kestra://` URI via `from`), applies the pattern to each line, and writes the structured results back to storage. Use it for batch log parsing or event normalization.
+
+Both tasks accept `pattern` for a single Grok expression or `patterns` for a list of expressions tried in order — matching stops at the first successful pattern. Add custom pattern definitions with `patternDefinitions` (a map of name to regex) or point `patternsDir` at directories containing pattern files. By default only named capture groups are returned (`namedCapturesOnly: true`) and matching stops at the first successful pattern (`breakOnFirstMatch: true`).

plugin-transform-json/src/main/resources/doc/io.kestra.plugin.transform.jsonata.md

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+# How to use the Transform JSONata plugin
+
+Query and transform JSON data using [JSONata](https://jsonata.org/) expressions — a functional language for selecting, filtering, reshaping, and aggregating JSON structures.
+
+## Tasks
+
+`TransformValue` evaluates a JSONata `expression` against a single JSON string passed via `from` and returns the transformed result. Use it to reshape or extract values from a task output already in your flow.
+
+`TransformItems` reads a JSON or Ion file from Kestra internal storage (passed as a `kestra://` URI via `from`), evaluates the `expression` against each record, and writes the results back to storage. If the expression returns an array and `explodeArray` is `true` (the default), each array element is written as a separate record — set `explodeArray: false` to write the whole array as a single record instead. Use `TransformItems` for batch transformations over large datasets.

plugin-transform-records/src/main/resources/doc/io.kestra.plugin.transform.md

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+# How to use the Transform plugin
+
 These tasks let you reshape, filter, combine, flatten, and summarize structured data without writing custom code. They work both with in-memory records and with stored Ion files, so the same tasks can be used for small workflow variables and larger streamed datasets.
 
 ## Common Inputs And Outputs