Recover projects after update: expose app dir, import legacy Gradle projects (compat mode)

[tyron12233]

Fixes #1003, #1024, #1041, #1042 — projects "disappearing" from the picker after a Play update.

Root cause

The app keeps the same com.tyron.code applicationId across updates, so the external files dir survives — the data was never lost, just not surfaced. Two generations of project data exist on disk:

• v0.2.9 (legacy): getExternalFilesDir("Projects") → <external-files>/Projects/<name> — Gradle projects.
• New app: <external-files>/codeassist/projects/<workspace> — native-model projects.

What this does

1. Expose the whole external files dir. The DocumentsProvider and the "Open in file manager" action now expose getExternalFilesDir(null) (parent of both Projects/ and codeassist/), with a full file view, so legacy sources are browsable. The storage card, reveal action, and provider all resolve the same storageRoot.

2. Recover into the picker. ProjectManager.importLegacyProjects() (runs once, non-destructive) sweeps the legacy data dirs:

• current-format projects (e.g. an earlier internal-storage build) are copied verbatim;
• legacy Gradle projects are imported in compatibility mode via a new tolerant GradleImport reader of the settings/build scripts — extracting modules, plugin/module type, the android {} SDK/namespace, and dependencies {} coordinates+scopes — which authors a native workspace from them.

3. Set expectations. The Gradle import is best-effort: dependency versions aren't resolved and build-script logic is ignored, so a compatibility-mode project may show unresolved symbols and may not build until deps are re-added. This is surfaced as a per-project amber "Compatibility" chip and a dismissible first-run banner.

Backups now also sweep the legacy Projects/ dir.

Limitations

Full Gradle sync (resolving the dependency graph, build-script evaluation) is roadmap step 9 and not attempted here. Compatibility-mode projects are for recovering/editing code, not guaranteed to build as-is.

Tests

• GradleImportTest — parser (modules/types/SDK/deps/scopes) + end-to-end import that lists, flags compatibility, opens with the right modules, and has sources copied.
• ProjectManagerTest.importsLegacyProjectsFromAPreviousStorageLocation — current-format recovery.
• Verified :ide-core:test, :ide-ui/:ide-desktop compile, and :ide-android:compileDebugKotlin (clean aside from an unrelated untracked scratch file).

[my-garbage]

@tyron12233 Where is this roadmap you wrote about?
Maybe it should be mentioned in the readme.md