fix(installer): tell Kiro IDE users to enable MCP in Settings

PR #473 emitted only "Restart Kiro for MCP changes to take effect."
That note is incomplete for Kiro IDE users: the IDE ships with MCP
support disabled by default, so a freshly-written
~/.kiro/settings/mcp.json is ignored until the user opens Settings,
searches "MCP", and flips the "Kiro Agent: Configure MCP" dropdown to
"Enabled". The agent then reports "No MCP powers installed" and falls
back to grep/Read — which looks like an installer wiring bug but isn't.

Kiro CLI doesn't gate on this flag — it reads the same file without
any toggle — so the second note calls out which audience needs the
extra step.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/installer/targets/kiro.ts

@@ -79,7 +79,15 @@ class KiroTarget implements AgentTarget {
     files.push(writeSteeringEntry(loc));
     return {
       files,
-      notes: ['Restart Kiro for MCP changes to take effect.'],
+      // The IDE-only enable-MCP step is load-bearing: Kiro IDE ships
+      // with MCP support disabled by default, so even a valid
+      // `~/.kiro/settings/mcp.json` at the documented path is ignored
+      // until the user flips the toggle. Kiro CLI reads the same file
+      // without a gate, so we call out which audience this applies to.
+      notes: [
+        'Restart Kiro for MCP changes to take effect.',
+        'Kiro IDE: also enable MCP in Settings (search "MCP" → "Enabled"). Kiro CLI users can skip this step.',
+      ],
     };
   }