Document QUARTO_PROJECT_SCRIPT_PROGRESS and QUARTO_PROJECT_SCRIPT_QUIET env vars

Add two new environment variables from quarto-dev/quarto-cli#12444 to the
pre/post render scripts documentation and the environment variables reference.
These let scripts adapt their output based on progress display availability
and quiet mode.

Author: cderv

docs/advanced/environment-vars.qmd

@@ -89,5 +89,9 @@ ENV["QUARTO_DOCUMENT_PATH"]
 +--------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | `QUARTO_EXECUTE_INFO`                      | `QUARTO_EXECUTE_INFO` holds the path of a file containing a JSON object with [execution information for Quarto engines](./quarto-execute-info.qmd). This is accessible by code in executable code cells.                     |
 +--------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| `QUARTO_PROJECT_SCRIPT_PROGRESS`           | Set to `"1"` when progress output can be shown during [pre/post render scripts](/docs/projects/scripts.qmd) (e.g. rendering multiple files), `"0"` otherwise.                                  |
++--------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
+| `QUARTO_PROJECT_SCRIPT_QUIET`              | Set to `"1"` when the `--quiet` flag is active during [pre/post render scripts](/docs/projects/scripts.qmd), `"0"` otherwise.                                                                  |
++--------------------------------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 
 For more information on the JSON object referenced by `QUARTO_EXECUTE_INFO`, see [Quarto engine execution information](./quarto-execute-info.qmd).

docs/projects/scripts.qmd

@@ -60,6 +60,10 @@ The following environment variables are passed to pre and post-render scripts (n
 | `QUARTO_PROJECT_OUTPUT_DIR`   | Output directory                                                                                                                                                              |
 | `QUARTO_PROJECT_INPUT_FILES`  | Newline separated list of all input files being rendered (passed only to `pre-render`)                                                                                        |
 | `QUARTO_PROJECT_OUTPUT_FILES` | Newline separated list of all output files rendered (passed only to `post-render`).                                                                                           |
+| `QUARTO_PROJECT_SCRIPT_PROGRESS` | Set to `"1"` when progress output can be shown (e.g. rendering multiple files), `"0"` otherwise.                                                                           |
+| `QUARTO_PROJECT_SCRIPT_QUIET`    | Set to `"1"` when the `--quiet` flag is active, `"0"` otherwise.                                                                                                           |
+
+Scripts can use `QUARTO_PROJECT_SCRIPT_PROGRESS` and `QUARTO_PROJECT_SCRIPT_QUIET` to adapt their output, for example by suppressing progress indicators when running in quiet mode or when progress display is not available.
 
 The project metadata and render list will be re-computed after any pre-render scripts have executed, allowing them to modify this project data.
 For example, a pre-render script might generate additional `qmd` files or `ipynb` files that should be rendered.