fix(worker): reopen the notmuch handle so queries see new mail

A read-only notmuch handle is a Xapian snapshot taken when it is opened,
so it never observes a write made by another process afterwards. The
worker opened one handle and kept it for the process lifetime, which made
the sync script's `notmuch new` invisible: every query after startup was
answered from the index as it stood when the application launched.

The symptom was mail arriving while the window was open and not appearing
until a restart. It was not confined to the post-sync refresh, which is
what made it hard to place: a query typed by hand also found nothing,
since it hits the same handle. Tag writes were unaffected throughout,
because applyTags opens its own read-write handle per call.

Reopen in openReadOnly() rather than at each call site: every read path
begins by asking for the handle. A reopen failure is deliberately not
fatal, since the existing handle is still usable and answering from a
slightly stale index beats refusing to answer.

The suite could not reproduce this before: the test helper builds a fresh
worker per query, so it opens a fresh handle every time. The new test
holds one worker across two queries and indexes between them from a
second process.

Item 104.

0 files changed, 0 insertions, 0 deletions