fix: paginate mailbox retrieval beyond maxObjectsInGet

[pirate]

Design

Paginate folder retrieval and ensure parent folders are sent to frontend before nested child folders.

• Mailbox/query returns parent-first ID pages with sortAsTree, bounded by the server-advertised maxObjectsInGet.
• Each ID page feeds Mailbox/get through a result reference in the same JMAP request. Request count scales by page, never by folder.
• The first page records the total and query state. Every page must preserve that state, contain only unique string IDs, and return the requested object count; otherwise the snapshot is rejected.
• Primary, delegated, and shared accounts use the same complete loader before mailbox mapping and tree construction.
• The sidebar builds the complete tree once, flattens expanded nodes parent-first, and mounts 250 rows at a time. Each rendered child therefore has its parent earlier in the rendered prefix.
• The complete mailbox model remains available while additional 250-row batches are revealed on demand. Fresh profiles with more than 1,000 mailboxes begin collapsed.

Capped object slice

Complete parent-first hierarchy

Validation

• Stalwart + Playwright integration tests: one parent and 520 children load with correct parent IDs and indentation
• Vitest suites: 40 tests pass, including split hierarchies, server-clamped pages, missing or malformed IDs, and delegated-account namespacing.
• A disposable 20,000-folder model check built and flattened the hierarchy and selected its first 250 rows in 53 ms

[Copilot]

Pull request overview

This PR fixes incomplete mailbox hierarchy loading when a JMAP server caps Mailbox/get responses at maxObjectsInGet (e.g., Stalwart), by switching to a paginated Mailbox/query + result-referenced Mailbox/get approach that loads all mailbox ids and fetches them page-by-page.

Changes:

• Add a new getRawMailboxes() helper that paginates Mailbox/query and fetches each page via result-referenced Mailbox/get, rejecting inconsistent page results.
• Update getMailboxes() and getAllMailboxes() to use the new complete mailbox loader for both primary and delegated/shared accounts.
• Add/adjust Vitest coverage to validate pagination edge cases (split parent/child across pages, server page clamping, exact page multiples, later-page failures, and shared-account id namespacing).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
lib/jmap/client.ts	Implements mailbox pagination via Mailbox/query + result-reference Mailbox/get and routes mailbox loaders through it.
lib/tests/jmap-recipient-mailboxes.test.ts	Updates mocks/docs to allow mailbox loading via query+get.
lib/tests/jmap-mailbox-pagination.test.ts	Adds dedicated tests for pagination correctness and failure handling.
lib/tests/jmap-draft-lifecycle.test.ts	Updates request mocking to answer mailbox loading via query+get.

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