Python deps: smart missing-package hint + switch to .vrf requirements file

Option A: when a {python} cell fails with ModuleNotFoundError/ImportError, the
log now suggests the exact PyPI package to add (with a module->package map, e.g.
cv2 -> opencv-python, sklearn -> scikit-learn), names the Verso requirements
file, and notes it could instead be a local module — so the langmuirthermalstudy
case isn't mistaken for a PyPI package.

Switch the per-project requirements file from requirements.txt to a Verso-
specific requirements.vrf (so it won't be confused with arbitrary .txt files);
QuartoRunner now looks for requirements.vrf, and 'vrf' is registered as an
editable text extension. The dedicated in-UI editor (and hiding it from the
file tree) follows in a separate change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/web/config/settings.defaults.js

@@ -56,6 +56,7 @@ const defaultTextExtensions = [
   'rmd',
   'qmd',
   'typ',
+  'vrf', // Verso requirements file (Python deps for Quarto venvs)
   'lua',
   'py',
   'gv',

services/web/frontend/js/ide/log-parser/quarto-log-parser.ts

@@ -37,6 +37,25 @@ const R_QUITTING_REGEX = /^Quitting from lines? (\d+)(?:-\d+)?\s*(?:\(([^)]+)\))
 //   ImportError: No module named scipy
 const PY_MODULE_REGEX =
   /^(?:ModuleNotFoundError|ImportError): No module named ['"]?([\w.]+)['"]?/
+// Import (module) name -> PyPI package name, for the common cases where they
+// differ. Anything not listed defaults to the module name itself.
+const PY_MODULE_TO_PACKAGE: Record<string, string> = {
+  cv2: 'opencv-python',
+  sklearn: 'scikit-learn',
+  skimage: 'scikit-image',
+  PIL: 'Pillow',
+  yaml: 'PyYAML',
+  bs4: 'beautifulsoup4',
+  Crypto: 'pycryptodome',
+  OpenSSL: 'pyOpenSSL',
+  dateutil: 'python-dateutil',
+  dotenv: 'python-dotenv',
+  serial: 'pyserial',
+  usb: 'pyusb',
+  cairo: 'pycairo',
+  gi: 'PyGObject',
+  win32com: 'pywin32',
+}
 // A typst diagnostic location line: `  ┌─ main.typ:5:10` / `  --> main.typ:5:10`
 const TYPST_LOCATION_REGEX = /(?:[┌╭]─|-->)\s*(.+?):(\d+):(\d+)/
 
@@ -77,17 +96,23 @@ export default function parseQuartoLog(rawLog: string): ParseResult {
     // through as an opaque error (or not be surfaced at all).
     const pyModule = trimmed.match(PY_MODULE_REGEX)
     if (pyModule) {
-      const pkg = pyModule[1]
+      const moduleName = pyModule[1]
+      // Suggest the PyPI package for the top-level module (cv2 -> opencv-python).
+      const topLevel = moduleName.split('.')[0]
+      const suggestion = PY_MODULE_TO_PACKAGE[topLevel] || topLevel
       data.push({
         line: pendingLocation.line ?? null,
         file: pendingLocation.file,
         level: 'error',
-        message: `Python package "${pkg}" is not installed on the server`,
+        message: `Python module "${moduleName}" is not available`,
         content:
-          `${clean}\n\nThe Python package "${pkg}" is not available in the ` +
-          `compile environment. Common scientific packages (numpy, pandas, ` +
-          `scipy, matplotlib, seaborn, scikit-learn, sympy, plotly) are ` +
-          `pre-installed; others must be added to the server image.`,
+          `${clean}\n\n` +
+          `If "${topLevel}" is a PyPI package, add \`${suggestion}\` to your ` +
+          `Verso requirements file (requirements.vrf) and recompile as the ` +
+          `project owner or a collaborator. If it is your own module, add its ` +
+          `.py file(s) to the project instead.\n` +
+          `Pre-installed: numpy, pandas, scipy, matplotlib, seaborn, ` +
+          `scikit-learn, sympy, plotly, tabulate, opencv-python (cv2), tqdm.`,
         raw: clean,
       })
       pendingLocation = {}