fix: batch directory-modal project fetch instead of N+1 getProject burst

Every directory picker (AddDocumentsModal, UseWorkflowModal, the assistant
project selector) loads its "Projects" tab through useDirectoryData, which
fired one GET /projects/:id for EVERY existing project the moment the modal
opened. Each of those requests costs an auth verification against GoTrue
plus ~6 PostgREST queries, so an account with N projects produced an
~8xN-request burst on the Supabase gateway per modal open.

Under that burst the gateway genuinely falls over: measured locally against
the Supabase CLI stack, overlapping modal-open storms drove GoTrue into
Postgres connection exhaustion ("failed to connect ... context deadline
exceeded") and produced 467x 500 + 641x 504 on /auth/v1/user in a single
run - surfacing to users as failed project creates/loads, and to the e2e
suite as the intermittent Kong 502s its specs currently retry around.

Fix: GET /projects now accepts ?include=documents and returns each
project's documents from one batched query (same attach helpers as
GET /projects/:id, run once across all documents), and useDirectoryData
uses it. A modal open is now 1 API request and a fixed number of DB
queries regardless of project count. After the change the same storm
harness produced zero 5xx and zero auth failures.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>