check-types fails on main for the browser extension: textContent (string | null) passed where string is required

[addyCooks]

Summary

bun run check-types fails on main for apps/browser-extension with a type
error that is unrelated to #1552. CONTRIBUTING.md instructs contributors to run
bun run check-types before submitting, so this is hit by anyone following the
documented workflow.

Error

apps/browser-extension/utils/ui-components.ts(611,13): error TS2345:
Argument of type '{ id: string; name: string | null; containerTag: string; }'
is not assignable to parameter of type '{ id: string; name: string; containerTag: string; }'.
Types of property 'name' are incompatible.
Type 'null' is not assignable to type 'string'.

Cause

createProjectSelectionModal declares its callback with a non-nullable name
(utils/ui-components.ts:405-411):

onImport: (project: { id: string; name: string; containerTag: string }) => void

The call site passes Node.textContent, which is string | null
(utils/ui-components.ts:604-611):

name: selectedOption.textContent,

WXT's generated tsconfig sets strict: true, so strictNullChecks rejects it.

Why it has gone unnoticed

1. CI does not type-check this package .github/workflows/ci.yml filters to
   @supermemory/ai-sdk and @supermemory/memory-graph only.
2. check-types for this app was already failing for the unrelated reason in
   check-types in the browser extension breaks whenever a file is added to public/ until you re-run bun install #1552, so a clean run was rare.
3. It is TypeScript-version-sensitive: TS 5.9's DOM lib does not widen this
   access to | null, but bun.lock pins typescript 5.8.3 (single entry; the
   extension's ^5.8.3 dedupes onto it), so the locked toolchain does hit it.

Runtime impact

None. textContent returns null only for node types such as document and
doctype; on an <option> element it is always a string. A disabled placeholder
option is always appended (utils/ui-components.ts:508-513), so select.options
is never empty and selectedIndex cannot be -1, and the if (selectedOption.value)
guard filters that placeholder out. This is a type-safety defect only.

Suggested fix

-    name: selectedOption.textContent,
+    name: selectedOption.textContent ?? "",

Relationship to other issues

#1446 added check-types coverage for this workspace but the app was never made
to pass, so the task is red on main. Fixing this completes that work. Separate
from #1552, which is about .wxt types going stale.

[linear-code]

ENG-1212