Make dev container bind mount work from git worktrees

The dev container's docker-compose.yml mounted `../..` (the directory two
levels above .devcontainer/) as `/workspaces`, relying on the repository
being checked out into a directory literally named `oracle-enhanced` so
that `workspaceFolder: /workspaces/oracle-enhanced` resolves.

When the dev container is opened from a git worktree (e.g.
`<repo>/.worktrees/<branch>/`), `../..` resolves to `.worktrees/` instead
of a parent containing `oracle-enhanced/`. Docker then auto-creates an
empty `/workspaces/oracle-enhanced` mount target on the host, so
`postCreateCommand: bash .devcontainer/postCreateCommand.sh` fails with
"No such file or directory".

Mount the directory containing .devcontainer/ directly as
`/workspaces/oracle-enhanced` so it does not depend on the host
directory's name. This works from both the main checkout and any
worktree.

Author: yahonda

.devcontainer/docker-compose.yml

@@ -4,7 +4,7 @@ services:
       context: .
       dockerfile: Dockerfile
     volumes:
-      - ../..:/workspaces:cached
+      - ..:/workspaces/oracle-enhanced:cached
     command: sleep infinity
     network_mode: service:oracle