Complete comprehensive Codex → LLMX branding update

Fixed all remaining user-facing "Codex" references across entire codebase:
- Updated all UI strings and error messages
- Fixed GitHub issue templates and workflows
- Updated MCP server tool descriptions and error messages
- Fixed all test messages and comments
- Updated documentation comments
- Changed auth keyring service name to "LLMX Auth"

Reduced from 201 occurrences to only code identifiers (struct/type names).
Changes span 78 files across Rust, Python, YAML, and JSON.

🤖 Generated with Claude Code

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

llmx-rs/mcp-server/tests/common/mcp_process.rs

@@ -162,7 +162,7 @@ impl McpProcess {
                     },
                     "serverInfo": {
                         "name": "codex-mcp-server",
-                        "title": "Codex",
+                        "title": "LLMX",
                         "version": "0.0.0",
                         "user_agent": user_agent
                     },

llmx-rs/mcp-server/tests/suite/llmx_tool.rs

@@ -42,7 +42,7 @@ const DEFAULT_READ_TIMEOUT: std::time::Duration = std::time::Duration::from_secs
 async fn test_shell_command_approval_triggers_elicitation() {
     if env::var(CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR).is_ok() {
         println!(
-            "Skipping test because it cannot execute when network is disabled in a Codex sandbox."
+            "Skipping test because it cannot execute when network is disabled in an LLMX sandbox."
         );
         return;
     }
@@ -173,7 +173,7 @@ fn create_expected_elicitation_request(
     codex_event_id: String,
 ) -> anyhow::Result<JSONRPCRequest> {
     let expected_message = format!(
-        "Allow Codex to run `{}` in `{}`?",
+        "Allow LLMX to run `{}` in `{}`?",
         shlex::try_join(command.iter().map(std::convert::AsRef::as_ref))?,
         workdir.to_string_lossy()
     );
@@ -207,7 +207,7 @@ fn create_expected_elicitation_request(
 async fn test_patch_approval_triggers_elicitation() {
     if env::var(CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR).is_ok() {
         println!(
-            "Skipping test because it cannot execute when network is disabled in a Codex sandbox."
+            "Skipping test because it cannot execute when network is disabled in an LLMX sandbox."
         );
         return;
     }
@@ -405,7 +405,7 @@ fn create_expected_patch_approval_elicitation_request(
     if let Some(r) = &reason {
         message_lines.push(r.clone());
     }
-    message_lines.push("Allow Codex to apply proposed code changes?".to_string());
+    message_lines.push("Allow LLMX to apply proposed code changes?".to_string());
 
     Ok(JSONRPCRequest {
         jsonrpc: JSONRPC_VERSION.into(),