feat: expand magic prompts coverage and split generation prompts (#835)

- Add configurable visible/instructions prompt families for commit/PR generation, PR checks/comments flows, and git conflict resolution helpers.
- Refactor prompt sending to explicit visible + synthetic parts instead of newline-based splitting, with legacy override migration for old keys.
- Polish Magic Prompts settings UX with grouped sidebar entries, tooltip-based descriptions, AI icon, and validation that visible prompts cannot be empty across web and VS Code runtimes.

packages/web/server/lib/magic-prompts/routes.js

@@ -0,0 +1,63 @@
+import { createMagicPromptRuntime } from './runtime.js';
+
+export const registerMagicPromptRoutes = (app, dependencies) => {
+  const {
+    fsPromises,
+    path,
+    openchamberDataDir,
+  } = dependencies;
+
+  const runtime = createMagicPromptRuntime({
+    fsPromises,
+    path,
+    filePath: path.join(openchamberDataDir, 'magic-prompts.json'),
+  });
+
+  app.get('/api/magic-prompts', async (_req, res) => {
+    try {
+      const state = await runtime.readPromptState();
+      res.json(state);
+    } catch (error) {
+      res.status(500).json({ error: error instanceof Error ? error.message : 'Failed to read magic prompts' });
+    }
+  });
+
+  app.put('/api/magic-prompts/:id', async (req, res) => {
+    const id = typeof req.params?.id === 'string' ? req.params.id : '';
+    const text = typeof req.body?.text === 'string' ? req.body.text : null;
+    if (text === null) {
+      return res.status(400).json({ error: 'text is required' });
+    }
+
+    try {
+      const state = await runtime.setOverride(id, text);
+      return res.json(state);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      const status = message.includes('Invalid prompt id') || message.includes('too long') || message.includes('cannot be empty') ? 400 : 500;
+      return res.status(status).json({ error: message });
+    }
+  });
+
+  app.delete('/api/magic-prompts/:id', async (req, res) => {
+    const id = typeof req.params?.id === 'string' ? req.params.id : '';
+    try {
+      const state = await runtime.resetOverride(id);
+      return res.json(state);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      const status = message.includes('Invalid prompt id') ? 400 : 500;
+      return res.status(status).json({ error: message });
+    }
+  });
+
+  app.delete('/api/magic-prompts', async (_req, res) => {
+    try {
+      const state = await runtime.resetAllOverrides();
+      return res.json(state);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      return res.status(500).json({ error: message || 'Failed to reset magic prompts' });
+    }
+  });
+};