feat(tui): add usage overlay and sidebar for displaying usage statistics and tasks

feat(tui): implement status bar with connection and turn state indicators
feat(tui): create workflow panel for agent status and progress visualization
feat(web): introduce web frontend interface with static file serving
feat(ws): add WebSocket interface for real-time communication and session management

apps/infrastructure/src/tools/lsp/diagnostics.rs

@@ -0,0 +1,49 @@
+//! Get diagnostics from LSP.
+
+use crate::tools::{Tool, ToolCtx};
+use anyhow::Result;
+use serde_json::{json, Value};
+
+pub struct LspDiagnostics;
+
+impl Tool for LspDiagnostics {
+    fn name(&self) -> &'static str {
+        "lsp_diagnostics"
+    }
+
+    fn description(&self) -> &'static str {
+        "Get diagnostics (errors, warnings) from the LSP for a file"
+    }
+
+    fn parameters(&self) -> Value {
+        json!({
+            "type": "object",
+            "properties": {
+                "language": {
+                    "type": "string",
+                    "description": "Language identifier"
+                },
+                "path": {
+                    "type": "string",
+                    "description": "File path to get diagnostics for"
+                }
+            },
+            "required": ["language", "path"]
+        })
+    }
+
+    fn run(&self, ctx: &ToolCtx, args: &Value) -> Result<String> {
+        let language = crate::tools::arg_str(args, "language")?;
+        let path = crate::tools::arg_str(args, "path")?;
+
+        let manager = ctx.lsp_manager.lock().unwrap();
+        if let Some(client) = manager.get_client(&language) {
+            let result = client.send_request("textDocument/diagnostic", &json!({
+                "textDocument": { "uri": format!("file://{}", path) }
+            }))?;
+            Ok(serde_json::to_string_pretty(&result)?)
+        } else {
+            anyhow::bail!("no LSP client connected for '{language}'")
+        }
+    }
+}