fix(modules): guard the portal's nav icon, resolve MODULES_DIR absolutely

Both found by the §7.7 browser smoke, running the slice-3 pair together, and
neither is visible to any test in either repo.

`PlayerPortalLayout` rendered `<n.icon />` unguarded while `AdminLayout` guarded
its equivalent. `icon` is optional in the nav contract, and every core row in
that sidebar has always had one — so the difference cost nothing until a module
registered a row without, and then it was not a missing glyph, it was React
error #130 and a blank player portal. Guarded now, like its neighbour.

`MODULES_DIR` is resolved absolute. `resolveClient` checks containment by
comparing an absolute `path.resolve(dir, entry)` against the module directory,
so a RELATIVE `MODULES_DIR` — which is what §7.7's own recipe produces when run
from `server/` — failed every module with "client.entry escapes the module
directory". A perfectly-placed entry, and a message pointing at the module.

Co-Authored-By: Claude <noreply@anthropic.com>

client/src/routes/player/PlayerPortalLayout.jsx

@@ -137,7 +137,13 @@ export default function PlayerPortalLayout() {
                 borderLeft: `2px solid ${isActive ? 'var(--accent)' : 'transparent'}`,
               })}
             >
-              <n.icon />
+              {/* Guarded, like AdminLayout's. `icon` is optional in the nav
+                  contract (§3.3) and every CORE row here has always had one, so
+                  an unguarded `<n.icon />` was fine right up until a module
+                  registered a row without — and then it was not a missing glyph,
+                  it was React error #130 and a blank portal. Found by the §7.7
+                  browser smoke; no DOM-less test can see it. */}
+              {n.icon && <n.icon />}
               <span>{n.label}</span>
             </NavLink>
           ))}

server/src/modules/loader.js

@@ -45,7 +45,14 @@ const { splitStatements } = require('../utils/sqlStatements')
 const log = require('../utils/logger')('modules')
 
 const REPO_ROOT = path.join(__dirname, '..', '..', '..')
-const MODULES_DIR = process.env.MODULES_DIR || path.join(REPO_ROOT, 'modules')
+// Resolved absolute, and the `path.resolve` is load-bearing rather than tidy.
+// `resolveClient` compares an absolute `path.resolve(dir, entry)` against this
+// directory to check containment, so a RELATIVE `MODULES_DIR` — which is what
+// anyone following §7.7's smoke recipe from `server/` naturally types — makes
+// that comparison fail for every module, with the thoroughly misleading
+// "client.entry escapes the module directory". Found the first time the smoke
+// was run against a module with a real client half.
+const MODULES_DIR = path.resolve(process.env.MODULES_DIR || path.join(REPO_ROOT, 'modules'))
 
 // One segment, lowercase, no parameters. A module prefix that could contain a
 // `/` or a `:` would let a module reach outside the slot it was given.