docs: link static plugin implementation as plugin API example (#642)

* docs: link static plugin implementation as plugin API example

The static file plugin is now open source. Link its implementation from
the Static Files overview (source of truth for behavior) and from the
Plugin API page (real-world example of the modern plugin API).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* docs: hyphenate "open-source" compound modifier

Review feedback on #642: "open source implementation" uses a compound
modifier before a noun, which takes a hyphen.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: Ethan-Arrowood

reference/components/plugin-api.md

@@ -381,7 +381,7 @@ Function signature for the `'all'` event handler passed to `scope.handleEntry()`
 
 ## Example: Static File Server Plugin
 
-A simplified form of the built-in `static` plugin demonstrating key Plugin API patterns:
+A simplified form of the built-in `static` plugin demonstrating key Plugin API patterns. For a complete, production example of this API in action, read the plugin's open-source implementation in [`server/static.ts`](https://github.com/HarperFast/harper/blob/main/server/static.ts).
 
 ```js
 export function handleApplication(scope) {

reference/static-files/overview.md

@@ -19,6 +19,8 @@ The `static` built-in plugin serves static files from your Harper application ov
 
 `static` does **not** need to be installed — it is built into Harper and only needs to be declared in your `config.yaml`.
 
+The plugin is open source: its implementation in [`server/static.ts`](https://github.com/HarperFast/harper/blob/main/server/static.ts) is the source of truth for the behavior described on this page.
+
 ## Basic Usage
 
 Configure `static` with the `files` option pointing to the files you want to serve: