chore: Remove OpenAI branding and references

Update project branding to reflect community fork status:

- Changed welcome message from "OpenAI's command-line coding agent"
  to "your command-line coding agent"
- Updated system prompt from "led by OpenAI" to "community project"
- Removed broken developers.openai.com/llmx documentation URLs
- Updated Windows setup instructions with correct npm package name
- Removed OpenAI CLA (not applicable to community fork)
- Removed OpenAI open source fund documentation
- Updated config docs to remove managed configuration references
- Changed npm package reference from @openai/llmx to @valknarthing/llmx

These changes complete the rebranding from OpenAI's project to an
independent community fork while maintaining proper attribution to
the original project in README.md.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

llmx-rs/core/prompt.md

@@ -1,4 +1,4 @@
-You are a coding agent running in the LLMX CLI, a terminal-based coding assistant. LLMX CLI is an open source project led by OpenAI. You are expected to be precise, safe, and helpful.
+You are a coding agent running in the LLMX CLI, a terminal-based coding assistant. LLMX CLI is an open source community project. You are expected to be precise, safe, and helpful.
 
 Your capabilities:
 

llmx-rs/tui/src/onboarding/welcome.rs

@@ -69,7 +69,7 @@ impl WidgetRef for &WelcomeWidget {
             "  ".into(),
             "Welcome to ".into(),
             "LLMX".bold(),
-            ", OpenAI's command-line coding agent".into(),
+            ", your command-line coding agent".into(),
         ]));
 
         Paragraph::new(lines)

llmx-rs/tui/src/onboarding/windows.rs

@@ -33,11 +33,8 @@ pub(crate) const WSL_INSTRUCTIONS: &str = r#"Install WSL2 by opening PowerShell
     nvm install 22
 
     # Install and run LLMX in WSL
-    npm install --global @openai/llmx
-    llmx
-
-    # Additional details and instructions for how to install and run LLMX in WSL:
-    https://developers.openai.com/llmx/windows"#;
+    npm install --global @valknarthing/llmx
+    llmx"#;
 
 pub(crate) struct WindowsSetupWidget {
     pub llmx_home: PathBuf,
@@ -102,7 +99,6 @@ impl WidgetRef for &WindowsSetupWidget {
                 "To use all LLMX features, we recommend running LLMX in Windows Subsystem for Linux (WSL2)".bold(),
             ]),
             Line::from(vec!["  ".into(), "WSL allows LLMX to run Agent mode in a sandboxed environment with better data protections in place.".into()]),
-            Line::from(vec!["  ".into(), "Learn more: https://developers.openai.com/llmx/windows".into()]),
             Line::from(""),
         ];