docs: explain Teams API limitation for message deletion

- Microsoft Teams Graph API does not support DELETE on channel messages
- This is a platform limitation, not an application error
- Updated UI to show clear warning about Teams API limitation
- Updated error messages to guide users on alternatives:
  - Delete via Teams client UI
  - Use delegated token with ChatMessage.ReadWrite.All permission
- HTTP 405 (Method Not Allowed) is the expected response from Graph API

server.ts

@@ -4,6 +4,7 @@ import { serveStatic } from 'hono/bun';
 import { cors } from 'hono/cors';
 import PocketBase from 'pocketbase';
 import { Client } from '@microsoft/microsoft-graph-client';
+import { listTeamChannels, listChannelMessages, listTeamChannelsWithToken, listChannelMessagesWithToken, deleteChannelMessage, deleteChannelMessageWithToken } from './services/teams/messages.ts';
 import { mkdir, appendFile } from 'fs/promises';
 import { existsSync } from 'fs';
 import path from 'path';
@@ -753,6 +754,88 @@ app.get('/api/health', (c) => {
   });
 });
 
+// List channels in a Team (to obtain Channel IDs)
+app.get('/api/teams/:teamId/channels', async (c) => {
+  const teamId = c.req.param('teamId');
+  try {
+    const authHeader = c.req.header('authorization') || c.req.header('Authorization');
+    const bearer = authHeader?.startsWith('Bearer ') ? authHeader.slice(7) : null;
+    const channels = bearer
+      ? await listTeamChannelsWithToken(teamId, bearer)
+      : await listTeamChannels(teamId);
+    return c.json({ success: true, teamId, channels });
+  } catch (err: any) {
+    console.error('⚠️ Failed to list channels:', err);
+    await logError('Graph List Channels', err, { teamId });
+    return c.json({ success: false, message: err.message || 'Failed to list channels' }, 500);
+  }
+});
+
+// List messages in a channel (to obtain message IDs)
+app.get('/api/teams/:teamId/channels/:channelId/messages', async (c) => {
+  const teamId = c.req.param('teamId');
+  const channelId = c.req.param('channelId');
+  const top = Number(c.req.query('top') || '50');
+  try {
+    const authHeader = c.req.header('authorization') || c.req.header('Authorization');
+    const bearer = authHeader?.startsWith('Bearer ') ? authHeader.slice(7) : null;
+    const messages = bearer
+      ? await listChannelMessagesWithToken(teamId, channelId, Math.min(top, 50), bearer)
+      : await listChannelMessages(teamId, channelId, Math.min(top, 50));
+    return c.json({ success: true, teamId, channelId, count: messages.length, messages });
+  } catch (err: any) {
+    console.error('⚠️ Failed to list messages:', err);
+    await logError('Graph List Messages', err, { teamId, channelId });
+    return c.json({ success: false, message: err.message || 'Failed to list messages' }, 500);
+  }
+});
+
+// Delete a message in a channel (requires appropriate Graph permissions)
+app.delete('/api/teams/:teamId/channels/:channelId/messages/:messageId', async (c) => {
+  const teamId = c.req.param('teamId');
+  const channelId = c.req.param('channelId');
+  const messageId = c.req.param('messageId');
+  try {
+    const authHeader = c.req.header('authorization') || c.req.header('Authorization');
+    const bearer = authHeader?.startsWith('Bearer ') ? authHeader.slice(7) : null;
+    const tokenType = bearer ? 'Bearer token provided' : 'Using app credentials';
+    console.log(`🗑️ DELETE request: ${tokenType} | Team: ${teamId} | Channel: ${channelId} | Message: ${messageId}`);
+    if (bearer) {
+      await deleteChannelMessageWithToken(teamId, channelId, messageId, bearer);
+    } else {
+      await deleteChannelMessage(teamId, channelId, messageId);
+    }
+    console.log(`✅ Successfully deleted message: ${messageId}`);
+    return c.json({ success: true, teamId, channelId, messageId });
+  } catch (err: any) {
+    const errMsg = err?.message || JSON.stringify(err);
+    const errStatus = err?.status || err?.statusCode;
+    
+    // Check if it's the Teams API limitation error
+    const isTeamsLimitation = errMsg?.includes('Teams API limitation') || errMsg?.includes('not supported');
+    
+    console.error(`${isTeamsLimitation ? '⚠️' : '❌'} Failed to delete message: ${errMsg} | Status: ${errStatus}`);
+    if (isTeamsLimitation) {
+      console.log(`📝 Note: This is a Microsoft Teams platform limitation, not an application error`);
+    }
+    
+    await logError('Graph Delete Message', err, { 
+      teamId, 
+      channelId, 
+      messageId, 
+      error: errMsg, 
+      status: errStatus,
+      isTeamsLimitation 
+    });
+    
+    return c.json({ 
+      success: false, 
+      message: errMsg || 'Failed to delete message',
+      isTeamsLimitation: isTeamsLimitation || false
+    }, 500);
+  }
+});
+
 // Test route: sends an exact sample Adaptive Card payload (no envelope)
 app.post('/api/test-notification', async (c) => {
   const webhook = process.env.POWER_AUTOMATE_WEBHOOK_URL || process.env.TEAMS_WEBHOOK_URL;