Add today-view plugin with Tana, ICS, and Donetick data sources

Implements an e-ink daily dashboard plugin ("today") with four sections:
date/focus/success header, agenda timeline, chores checklist, and
due/overdue task lists.

Data sources:
- Focus & success text: Tana daily note (src/sources/tana.ts)
- Due/overdue tasks: Tana task search (src/sources/tana.ts)
- Agenda events: ICS calendar feeds (src/sources/ics.ts)
- Chores: Donetick API (src/sources/donetick.ts)

All sources fetch in parallel and fall back gracefully on error.
Tests use mock HTTP servers with synthetic data — no real services needed.

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

src/preview.ts

@@ -0,0 +1,96 @@
+import puppeteer from 'puppeteer-core';
+import { devices } from './devices';
+import { createPlugin } from './plugins';
+import { render } from './template';
+
+const args = process.argv.slice(2);
+
+if (args.includes('--help') || args.includes('-h')) {
+  console.log(`Usage: bun run src/preview.ts [options]
+
+Render a plugin to a local PNG file for testing.
+
+Options:
+  --config <path>   Config file (default: config.json)
+  --device <id>     Device ID from config (default: first device)
+  --output <path>   Output PNG path (default: preview.png)
+  --firefox <path>  Firefox executable path (or set FIREFOX env var)
+  --dither          Apply e-ink dithering via ImageMagick
+  --html            Also save the raw HTML to <output>.html
+  -h, --help        Show this help`);
+  process.exit(0);
+}
+
+function getArg(flag: string, fallback: string): string {
+  const idx = args.indexOf(flag);
+  return idx !== -1 && args[idx + 1] ? args[idx + 1]! : fallback;
+}
+
+const configPath = getArg('--config', Bun.env['CONFIG_FILE'] ?? 'config.json');
+const outputPath = getArg('--output', 'preview.png');
+const firefoxPath = getArg('--firefox', Bun.env['FIREFOX'] ?? 'firefox');
+const dither = args.includes('--dither');
+const saveHtml = args.includes('--html');
+
+const config = JSON.parse(await Bun.file(configPath).text());
+const deviceEntries = Object.entries(config.devices ?? {});
+
+if (deviceEntries.length === 0) {
+  console.error('No devices found in config.');
+  process.exit(1);
+}
+
+const deviceIdArg = getArg('--device', '');
+const [deviceId, deviceConfig] = deviceIdArg
+  ? [deviceIdArg, config.devices[deviceIdArg]]
+  : (deviceEntries[0] as [string, any]);
+
+if (!deviceConfig) {
+  console.error(`Device "${deviceIdArg}" not found. Available: ${deviceEntries.map(([k]) => k).join(', ')}`);
+  process.exit(1);
+}
+
+const model = devices.find((a) => a.name === (deviceConfig.model ?? 'inkplate_10'));
+if (!model) {
+  console.error(`Unknown model: ${deviceConfig.model}`);
+  process.exit(1);
+}
+
+console.log(`Rendering plugin "${deviceConfig.plugin ?? 'calendar'}" for device "${deviceId}" (${model.width}x${model.height})...`);
+
+const plugin = createPlugin(deviceConfig.plugin ?? 'calendar', deviceConfig.settings ?? {});
+const html = await render([[plugin, 'full']], model);
+
+if (saveHtml) {
+  const htmlPath = outputPath.replace(/\.png$/, '.html');
+  await Bun.write(htmlPath, html);
+  console.log(`HTML saved to ${htmlPath}`);
+}
+
+const browser = await puppeteer.launch({
+  browser: 'firefox',
+  args: ['--new-instance'],
+  executablePath: firefoxPath,
+});
+
+const page = await browser.newPage();
+await page.setViewport({ width: model.width, height: model.height, deviceScaleFactor: 1 });
+await page.setContent(html, { waitUntil: 'networkidle2' });
+await Bun.sleep(3000);
+const screenshot = await page.screenshot({ encoding: 'binary' });
+await page.close();
+await browser.close();
+
+if (dither) {
+  const colormap = Bun.env['COLORMAP'] ?? './colormap.png';
+  const processed = await Bun.spawn(
+    ['magick', '-', '-dither', 'FloydSteinberg', '-remap', colormap,
+     '-define', 'png:bit-depth=2', '-define', 'png:color-type=0', '-strip', 'png:-'],
+    { stdin: screenshot }
+  ).stdout.bytes();
+  await Bun.write(outputPath, processed);
+} else {
+  await Bun.write(outputPath, screenshot);
+}
+
+console.log(`Preview saved to ${outputPath}`);