A test pins importing an origin's issue: one row per origin id, the local sequence pushed past its number

Contributing to an existing repository rests on importIssue in src/origins/import.ts, and no test imports it.

Done:

[ ] A new test drives importIssue against an in-memory app: importing the same remote issue twice leaves one row and reports created then not; a changed remote title updates that row
[ ] After importing remote #40, the repository's next native issue is numbered above 40
[ ] A blank remote title reads #<number>; a remote with pull set imports as a pull
[ ] No source file changes; if a case fails, the pull fixes the code and says which

Files: test/origins-import-issue.test.ts

Risks: the import context needs a repo and an actor; build them with the helpers other tests use, not new fixtures in src/.

Before pushing: bun x tsc --noEmit and bun test test/origins-import-issue.test.ts.

A test pins importing an origin's issue: one row per origin id, the local sequence pushed past its number #6654