feat(tui): add prompt history navigation with Up/Down arrows

- Browse previously submitted prompts using Up/Down arrow keys
- History is session-scoped and stores up to 100 entries
- Load history from session on continue/resume
- Includes 15 tests for history navigation

fixes #121

packages/coding-agent/src/tui/tui-renderer.ts

@@ -881,6 +881,22 @@ export class TuiRenderer {
 		}
 		// Clear pending tools after rendering initial messages
 		this.pendingTools.clear();
+
+		// Populate editor history with user messages from the session (oldest first so newest is at index 0)
+		for (const message of state.messages) {
+			if (message.role === "user") {
+				const textBlocks =
+					typeof message.content === "string"
+						? [{ type: "text", text: message.content }]
+						: message.content.filter((c) => c.type === "text");
+				const textContent = textBlocks.map((c) => c.text).join("");
+				// Skip compaction summary messages
+				if (textContent && !textContent.startsWith(SUMMARY_PREFIX)) {
+					this.editor.addToHistory(textContent);
+				}
+			}
+		}
+
 		this.ui.requestRender();
 	}