fix(pgpm): use workspace-level module detection for export flow

[pyramation]

fix(pgpm): use workspace-level module detection for export flow

Summary

Fixes "Not inside a module" error when running pgpm export from workspace root.

The previous implementation called getInstalledModules() which requires being inside a module directory. This PR:

1. Adds getWorkspaceInstalledModules() method to PgpmPackage that scans workspace/extensions/ directly without requiring module context
2. Splits the module detection/installation flow:
   • detectMissingModules() - workspace-level detection + user prompt (before module creation)
   • installMissingModules() - module-level installation (after module creation)
3. Updates preparePackage() to return the module directory path for use in installation
4. Extracts EXTENSIONS_DIR constant to centralize the extensions directory name

Updates since last revision

• Added EXTENSIONS_DIR constant at module level to avoid hardcoding 'extensions' string in multiple places
• Updated installModules(), getInstalledModules(), and getWorkspaceInstalledModules() to use the constant

Review & Testing Checklist for Human

• Test the fix: Run pgpm export from workspace root and verify it no longer throws "Not inside a module" error
• Verify scoped package detection: Check that getWorkspaceInstalledModules() correctly detects packages like @pgpm/base32 in extensions/@pgpm/base32/
• Verify installation still works: If you have missing modules, confirm the install prompt works and modules are installed into the correct module's package.json
• Check for other callers: Verify no other code depends on preparePackage() returning void

Recommended test plan:

1. Navigate to a pgpm workspace root (not inside a module)
2. Run pgpm export with a database that has migrations
3. Confirm the export completes without "Not inside a module" error
4. If prompted to install missing modules, confirm they install correctly

Notes

• This fix was not E2E tested due to lack of database seed data
• The flow change (detect before module creation, install after) is intentional to satisfy both workspace-level detection and module-level installation requirements

Link to Devin run: https://app.devin.ai/sessions/7e7813472a0643aa88ccb509b288050a
Requested by: Dan Lynch (@pyramation)

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring