Wire TypeScript interpreter module into state.ts, remove Go endpoint

[zackverham]

Summary

• Replaces api.interpreters.get() HTTP calls with in-process getInterpreterDefaults() from the TypeScript interpreter module (Add TypeScript interpreter detection module #3703)
• Adds requiresPython / requiresR fields to PythonConfig / RConfig types and fill-in logic in UpdateConfigWithDefaults
• Removes the Go /api/interpreters endpoint (get_interpreters.go) and its route registration
• Removes the Interpreters API resource class from the TypeScript client

Bug fix: requiresPython / requiresR were never applied to configurations

The Go FillDefaults methods (config/types.go) already populated requiresPython and requiresR on the interpreter response DTO. However, the TypeScript UpdateConfigWithDefaults only copied version, packageFile, and packageManager from the defaults — it silently dropped the requiresPython / requiresR fields. This PR adds the missing fill-in logic so these fields are actually applied to configurations for the first time.

---

This is PR 2 of 3 splitting up #3672. This is the behavioral switchover — can be reviewed independently of PR 3.

PRs: PR 1 (#3703, merged) | PR 2 (this) | PR 3 (#3705)

Test plan

• npx tsc --noEmit passes
• npx vitest run src/api/types/configurations.test.ts — 12 tests including 6 new tests for requiresPython / requiresR fill-in logic
• npx vitest run src/state.test.ts — 16 tests pass
• go test -short ./internal/services/api/... passes
• npx prettier --check passes
• CI passes

🤖 Generated with Claude Code

[christierney]

this (and the python equivalent below) seem obviously right, but I'm surprised this wasn't already here? This function predates the migration project. Was there an existing bug here?

[zackverham]

I think so, yeah - I believe this was a bug. I should add that to the PR description, sorry.

[christierney]

we're not just moving, we're improving!

[zackverham]

Smoke Test Plan

What changed

This PR replaces the HTTP call to the Go /api/interpreters endpoint with an in-process TypeScript call (getInterpreterDefaults()), removes the Go endpoint entirely, and adds requiresPython/requiresR fill-in logic to UpdateConfigWithDefaults.

Two code paths in state.ts are affected:

1. refreshConfigurations() — called on startup, when .posit/publish/*.toml files change, and on manual refresh
2. getSelectedConfiguration() — called when rendering content, refreshing packages, managing secrets, editing configs, deploying, etc.

Prerequisites

• A workspace with at least one .posit/publish/*.toml configuration that has a python and/or r section
• Python and/or R installed and on PATH
• Optionally: a project with .python-version, pyproject.toml, DESCRIPTION, or renv.lock for requiresPython/requiresR coverage

Test cases

1. Extension startup — Python project

1. Open a project that has a .posit/publish/*.toml config with a python section
2. The sidebar should load without errors
3. The Python packages panel should display — confirming python.version, python.packageFile, and python.packageManager were populated from the TypeScript detector

Pass: Sidebar renders, Python packages section shows the correct package file and packages. No errors in the Output panel.

2. Extension startup — R project

1. Open a project with a .posit/publish/*.toml config that has an r section
2. The R packages panel should display correctly

Pass: R packages section shows packages. No errors.

3. Configuration file change triggers refresh

1. With the extension running, edit a .posit/publish/*.toml file (e.g. change the title)
2. The file watcher should trigger refreshConfigurations()
3. The sidebar should update without errors

Pass: Changes reflected in sidebar. No errors in Output panel.

4. Selecting a deployment loads its configuration

1. If multiple deployments exist, switch between them in the sidebar
2. Each switch calls getSelectedConfiguration(), which invokes getInterpreterDefaults()

Pass: Configuration loads for each deployment. Python/R package sections update appropriately.

5. Python not on PATH

1. Temporarily rename/remove Python from PATH (or test on a machine without Python)
2. Open a project with a Python configuration

Pass: Extension loads without crashing. The Python section should still appear but with empty/default version. No unhandled exceptions.

6. R not on PATH

1. Same as above but for R

Pass: Extension loads without crashing. R section gracefully handles missing interpreter.

7. Mixed project (Python + R)

1. Open a project whose .toml config has both python and r sections
2. Both package panels should populate correctly

Pass: Both Python and R packages display. Both versions are detected.

8. Deploy still works

1. Select a deployment and click Deploy
2. The deployment should proceed — this exercises the full config-loading pipeline including interpreter defaults

Pass: Deployment completes successfully. The deployed configuration has correct interpreter versions.

9. Go endpoint is gone (negative test)

1. With the extension running, attempt to call GET /api/interpreters?dir=. directly via curl against the Go backend port

Pass: Returns 404 or "not found" — confirming the route was removed and nothing else depends on it.

10. requiresPython / requiresR populated

1. Create a project with a .python-version file (e.g. 3.11) and a DESCRIPTION file with Depends: R (>= 4.1.0)
2. Open the project and check the configuration that gets written during deployment

Pass: The requiresPython and requiresR fields are populated in the configuration defaults.

Automated coverage

Area	Coverage
UpdateConfigWithDefaults fill-in logic	configurations.test.ts (12 tests including 6 new)
state.ts mock paths	state.test.ts (16 tests)
Interpreter detection module	interpreters/*.test.ts (unit), integration.test.ts (PR #3705)