⚙️ [Maintenance]: Move coding standards to copilot-instructions and update parameter set naming guidelines (#551)

The coding standards document is moved from the repository root to the
standard `.github/copilot-instructions.md` location recognized by GitHub
Copilot, and the parameter set naming guidelines are updated with
clearer, more comprehensive rules.

## Copilot instructions location

The `CodingStandard.md` file is renamed to
`.github/copilot-instructions.md`, aligning with the standard location
for AI-assisted coding instructions. This is an internal maintenance
change — no code or shipped artifact is affected.

## Parameter set naming guidelines

The previous "Default Parameter Sets" section is replaced with a
comprehensive "Parameter Set Naming" section providing clearer rules:

- Functions with a single parameter set do not need a name or
`DefaultParameterSetName`.
- Functions with multiple parameter sets must use descriptive names that
tell the user what each set does.
- Generic names like `'__AllParameterSets'` or `'Default'` are
explicitly prohibited.
- Parameter sets should be named after the action or scope they
represent (e.g., `'List repositories for authenticated user'`).
- Public functions calling private functions should use the private
function's synopsis as the parameter set name.

Author: MariusStorhaug

CodingStandard.md .github/copilot-instructions.mdCodingStandard.md renamed to .github/copilot-instructions.md

@@ -31,9 +31,17 @@ Additions or adjustments to those defaults are covered in this document to ensur
   - Private function name format: **`Verb-GitHubNoun`** (same style but no aliases).
   - **`Get-`** functions must **not** include `[CmdletBinding(SupportsShouldProcess)]`. You only use `SupportsShouldProcess` on commands that change or remove data (`Set-`, `Remove-`, `Add-`, etc.).
 
-- **Default Parameter Sets**
-  - Do **not** declare `DefaultParameterSetName = '__AllParameterSets'`.
-  - Only specify a `DefaultParameterSetName` if it is actually different from the first parameter set.
+- **Parameter Set Naming**
+  - When a function has only one parameter set, a name is not needed and `DefaultParameterSetName` should not be set.
+  - When a function has multiple parameter sets, **every** parameter set **must** have a descriptive name that tells
+    the user what will happen when they use it. Set `DefaultParameterSetName` in the `[CmdletBinding()]` attribute to
+    the most commonly used parameter set.
+  - Do **not** use generic names like `'__AllParameterSets'` or `'Default'`.
+  - Name parameter sets after the action or scope they represent, e.g. `'List repositories for authenticated user'`,
+    `'Get a repository'`, `'List organization repositories'`.
+  - For public functions that call private functions, use the **synopsis** of the called private function as the
+    parameter set name (e.g. if the private function's synopsis is `List repositories for a user`, the parameter set
+    name becomes `'List repositories for a user'`).
 
 - **One API Call = One Function**
   - If you find that a single function is handling multiple distinct API calls, split it into multiple functions.