fix(session): resolve a rekeyed project before creating a session

[DeputyFifeofMayberry]

Issue for this PR

Closes #42734

Type of change

• Bug fix

What does this PR do?

Session.createNext used the project id cached on the instance context. When another opencode process rekeys a project (a git remote is added or changed), Project.fromDirectory migrates rows to the new id and deletes the previous project row. The still-running instance keeps the deleted id, so the projected session.created insert fails the session.project_id foreign key with FOREIGN KEY constraint failed.

This checks that the cached project row still exists and re-resolves the session directory through Project.fromDirectory when it does not, before publishing the event. The normal path is unchanged apart from one indexed lookup.

How did you verify your code works?

Added a regression test in packages/opencode/test/session/session.test.ts: it rekeys a temp git repo (adds a remote, calls fromDirectory) and then creates a session from the stale instance. Before the change the test fails with the issue's exact FK insert error; after, it passes.

Also ran:

• bun run typecheck in packages/opencode (clean)
• bun test test/session/session.test.ts test/project/project.test.ts test/project/project-directory.test.ts test/effect/instance-state.test.ts test/server/httpapi-session.test.ts test/server/global-session-list.test.ts — 89 pass, 0 fail

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR