Caused by #48763 and
#48800

Release Notes:

- N/A *or* Added/Fixed/Improved ...

…ce entity lease (#49058)

Closes #49055

**Heads up**: This might be a naïve solution. I ran into the issue after
merging latest main into
#48896, and confirming that it
was unrelated to that PR and incoming from upstream.

Agent one-shot the fix, it works and tests pass. But I'm still wrapping
my head around the changes that led to the bug. I figured the breakage
is bad enough (I couldn't open devcontainers at all) to submit a
possibly naïve fix.

## Fix 

Hoists the `find_devcontainer_configs` call out of `new_dev_container`
and into the call site, where we already have a direct `&mut Workspace`
reference that doesn't go through the entity map. The computed configs
are passed into `new_dev_container` as an argument.

## What was happening

After #48800 ("Re-add MultiWorkspace"), `with_active_or_new_workspace`
nests a `Workspace` entity lease inside a `MultiWorkspace` entity lease.
The `OpenDevContainer` handler was also changed from async to sync in
the same PR, so `RemoteServerProjects::new_dev_container` now runs while
`Workspace` is leased. Inside `new_dev_container`, a
`WeakEntity<Workspace>::read_with` call tries to read `Workspace`
through the entity map, finds it already leased, and panics.

Release Notes:

- Fixed a panic when opening the dev container modal via the
`OpenDevContainer` action.

Added 20 new actionable suggestions from merged PRs.

Processed ~60 PRs in this run:
- 20 actionable → queued
- ~39 unactionable (no docs needed)
- 1 failed (PR #48800: diff too large)