Add plan-confirm steps to all workflows, cite alphaXiv and Agent Computer, add visuals to writer

- Every workflow prompt now shows a plan and asks the user to confirm before executing
- /autoresearch asks for execution environment (local, branch, venv, cloud) and confirms before looping
- Writer agent and key prompts now generate charts (pi-charts) and diagrams (Mermaid) when data calls for it
- Cite alphaXiv and Agent Computer in README and website homepage
- Clear terminal screen before launching Pi TUI
- Remove Alpha Hub GitHub link in favor of alphaxiv.org

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/pi/launch.ts

@@ -12,6 +12,10 @@ export async function launchPiChat(options: PiRuntimeOptions): Promise<void> {
 		throw new Error(`Promise polyfill not found: ${promisePolyfillPath}`);
 	}
 
+	if (process.stdout.isTTY) {
+		process.stdout.write("\x1b[2J\x1b[3J\x1b[H");
+	}
+
 	const child = spawn(process.execPath, ["--import", promisePolyfillPath, piCliPath, ...buildPiArgs(options)], {
 		cwd: options.workingDir,
 		stdio: "inherit",