Improve how dev'ed packages are handled

[pfitzseb]

As per 🤖:

Dev'd (path-dependency) packages are handled statically by design: their symbols come from StaticLint's semantic pass over their source, and the parent never consumes their .jstore — even though the DJP child still loads them and writes one.

• layer_static_lint.jl:44 derived_deved_package_meta runs semantic_pass over the dev'd entry file's include closure and extracts its top-level module binding; layer_static_lint.jl:108-145 registers it in workspace_packages.
• StaticLint/imports.jl:208-209 resolves using DevedPkg to that CST binding before consulting the EnvStore (per-file mode does the equivalent through the module-tree context, imports.jl:219-225).
• The store side excludes them: types.jl:482-497 loads caches for regular_packages + stdlib_packages only, layer_environment.jl:149-172 builds the ExternalEnv from those same two groups, and the launch gate skips manifest entries with a "path" key (dynamic_feature.jl:524-525).

The bug

Both the static registration and the project_deps entry are gated on derived_has_file(<pkgdir>/src/<Name>.jl) (layer_environment.jl:179, :196), and derived_has_file is strict membership in input_files — workspace-folder files plus open documents (layer_files.jl:33-37). The lazy indirect-include mechanism (derived_has_content) is not used here.

So when the dev'd path lies outside every workspace folder, both paths miss: no .jstore is consumed (it's dev'd) and no static pass runs (its files aren't in the set). The name isn't even added to project_deps, so using Foo resolves to nothing and is reported as missing.

Repro

Open folder A/ whose Project.toml/Manifest.toml dev ../B, with B/ outside the workspace. In A/src/A.jl, using B is flagged, and B.anything gets no completions, hover, or go-to-def. Adding B/ as a second workspace folder fixes it.

Possible directions

1. Reach the dev'd entry closure through the lazy indirect-file input (derived_has_content) instead of derived_has_file, so out-of-workspace dev'd sources are read from disc.
2. Fall back to the dev'd package's .jstore — the DJP already writes one; only the parent-side loading and the input_package_metadata key (dev'd entries have no git_tree_sha1, sometimes no version) need work.
3. At minimum, add the name to project_deps unconditionally so using B isn't a false UnresolvedImport.