test: align inbox IPC handler coverage with domain delegation

[h4yfans]

What

• update apps/desktop/src/main/ipc/inbox-handlers.test.ts to match the desktop inbox domain delegation shape on memry/inbox-domain-extraction
• replace stale handler expectations that still assumed the older inline IPC implementation

Why

• this branch originally replayed a partial inbox extraction on top of a branch that already contains the broader extraction, which caused the merge conflict
• after rebasing onto memry/inbox-domain-extraction, the only meaningful remaining delta was test coverage that matches the newer transport-only handler boundary

How

• wrap the real createDesktopInboxDomain() in the test mock and override only the capture/retry commands under test
• keep the actual CRUD/query/batch handler wiring so the rest of the handler test file still exercises the rebased branch shape
• update stale assertions for image capture delegation and archive behavior to match the current implementation

Type

• feat
• fix
• refactor
• docs
• test
• chore

Test plan

• Unit tests added/updated
• Manual testing
• ./node_modules/.bin/vitest run --config config/vitest.config.ts --project main src/main/ipc/inbox-handlers.test.ts
• ./node_modules/.bin/eslint --no-warn-ignored src/main/ipc/inbox-handlers.test.ts

Screenshots

• N/A

Checklist

• Self-reviewed code
• Updated tests to match current behavior
• Resolved the branch conflict against memry/inbox-domain-extraction