fix: Rename .nf files to _main.nf to eliminate Astro warnings

Rename all main.nf files to _main.nf and update corresponding import 
statements to prevent Astro from treating pipeline files as pages.

- Rename: main.nf → _main.nf in all pipeline subdirectories
- Update imports: './main.nf?raw' → './_main.nf?raw' in all .mdx files
- Eliminates console warnings about unsupported file types
- Maintains functionality while following Astro conventions

Author: edmundmiller

src/pages/examples/basic-pipeline/main.nf renamed to src/pages/examples/basic-pipeline/_main.nf

@@ -4,7 +4,7 @@ layout: "@layouts/ExampleLayout.astro"
 ---
 
 import { Code } from "astro-expressive-code/components";
-import pipelineCode from "./main.nf?raw";
+import pipelineCode from "./_main.nf?raw";
 
 <div class="blg-summary example">
 <h2>Basic pipeline</h2>

src/pages/examples/basic-pipeline/index.mdx

@@ -4,7 +4,7 @@ layout: "@layouts/ExampleLayout.astro"
 ---
 
 import { Code } from "astro-expressive-code/components";
-import pipelineCode from "./main.nf?raw";
+import pipelineCode from "./_main.nf?raw";
 
 <div class="blg-summary example">
 <h2>BLAST pipeline</h2>

src/pages/examples/blast-pipeline/main.nf renamed to src/pages/examples/blast-pipeline/_main.nf

@@ -4,7 +4,7 @@ layout: "@layouts/ExampleLayout.astro"
 ---
 
 import { Code } from "astro-expressive-code/components";
-import pipelineCode from "./main.nf?raw";
+import pipelineCode from "./_main.nf?raw";
 
 <div class="blg-summary example">
 <h2>Machine Learning pipeline</h2>

src/pages/examples/blast-pipeline/index.mdx

@@ -4,7 +4,7 @@ layout: "@layouts/ExampleLayout.astro"
 ---
 
 import { Code } from "astro-expressive-code/components";
-import pipelineCode from "./main.nf?raw";
+import pipelineCode from "./_main.nf?raw";
 
 <div class="blg-summary example">
 <h2>Mixing scripting languages</h2>

src/pages/examples/machine-learning-pipeline/main.nf renamed to src/pages/examples/machine-learning-pipeline/_main.nf

@@ -4,7 +4,7 @@ layout: "@layouts/ExampleLayout.astro"
 ---
 
 import { Code } from "astro-expressive-code/components";
-import pipelineCode from "./main.nf?raw";
+import pipelineCode from "./_main.nf?raw";
 
 <div class="blg-summary example">
 <h2>RNA-Seq pipeline</h2>