Add Footgun Prompting feature documentation and sidebar entry (#104)

Author: hannesrudolph

docs/features/footgun-prompting.md

@@ -0,0 +1,51 @@
+---
+sidebar_label: 'Footgun Prompting'
+---
+
+# Footgun Prompting: Override System Prompts
+
+Footgun Prompting, AKA Overriding System Prompt, allows advanced users to completely replace the default system prompt for a specific Roo Code mode. This provides granular control over the AI's behavior but bypasses built-in safeguards.
+
+:::info **footgun** *(noun)*
+
+1.  *(programming slang, humorous, derogatory)* Any feature likely to lead to the programmer shooting themself in the foot.
+
+> The System Prompt Override is considered a footgun because modifying the core instructions without a deep understanding can lead to unexpected or broken behavior, especially regarding tool usage and response consistency.
+
+:::
+
+## How It Works
+
+1.  **Override File:** Create a file named `.roo/system-prompt-{mode-slug}` in your workspace root (e.g., `.roo/system-prompt-code` for the Code mode).
+2.  **Content:** The content of this file becomes the new system prompt for that specific mode.
+3.  **Activation:** Roo Code automatically detects this file. When present, it replaces most of the standard system prompt sections.
+4.  **Preserved Sections:** Only the core `roleDefinition` and any `customInstructions` you've set for the mode are kept alongside your override content. Standard sections like tool descriptions, rules, and capabilities are bypassed.
+5.  **Construction:** The final prompt sent to the model looks like this:
+    ```
+    ${roleDefinition}
+
+    ${content_of_your_override_file}
+
+    ${customInstructions}
+    ```
+
+## Accessing the Feature
+
+You can find the option and instructions within the Roo Code UI:
+
+1.  Click the <Codicon name="notebook" /> icon in the Roo Code top menu bar.
+2.  Expand the **"Advanced: Override System Prompt"** section.
+3.  Clicking the file path link within the explanation will open or create the correct override file for the currently selected mode in VS Code.
+
+<img src="/img/footgun-prompting/footgun-prompting.png" alt="UI showing the Advanced: Override System Prompt section" width="500" />
+
+
+## Key Considerations & Warnings
+
+-   **Intended Audience:** Best suited for users deeply familiar with Roo Code's prompting system and the implications of modifying core instructions.
+-   **Impact on Functionality:** Custom prompts override standard instructions, including those for tool usage and response consistency. This can cause unexpected behavior or errors if not managed carefully.
+-   **Mode-Specific:** Each override file applies only to the mode specified in its filename (`{mode-slug}`).
+-   **No File, No Override:** If the `.roo/system-prompt-{mode-slug}` file doesn't exist, Roo Code uses the standard system prompt generation process for that mode.
+-   **Directory Creation:** Roo Code ensures the `.roo` directory exists before attempting to read or create the override file.
+
+Use this feature cautiously. While powerful for customization, incorrect implementation can significantly degrade Roo Code's performance and reliability for the affected mode.

sidebars.ts

@@ -31,6 +31,7 @@ const sidebars: SidebarsConfig = {
         'features/custom-instructions',
         'features/custom-modes',
         'features/enhance-prompt',
+        'features/footgun-prompting',
         'features/model-temperature',
         {
           type: 'category',