Add `pnpm` support to JFrog modules (`jfrog-token`, `jfrog-oauth`)

[blinkagent]

Summary

JFrog CLI now natively supports pnpm via jf pnpm (install/publish with build-info tracking). We should add pnpm as a first-class package manager to the jfrog-token and jfrog-oauth modules in coder/registry, alongside the existing npm, go, pypi, docker, conda, and maven support.

References

• JFrog CLI PR: Support pnpm command for jfrog-cli jfrog/jfrog-cli#3390
• jfrog-cli-artifactory PR: Support pnpm command jfrog/jfrog-cli-artifactory#393
• Shipped in: https://github.com/jfrog/jfrog-cli/releases/tag/v2.98.0
• Docs: https://docs.jfrog.com/artifactory/docs/use-pnpm-with-jfrog-cli
• Supported versions (pnpm 10.x / 11.x, 11.x requires jf CLI >= 2.116.0): https://docs.jfrog.com/artifactory/docs/package-manager-compatibility-matrix

Requirements

• pnpm 10.x or 11.x (11.x needs JFrog CLI >= 2.116.0)
• Node.js 20+
• An npm-type Artifactory repository (reused for pnpm)
• .npmrc with registry URL + auth (same file pnpm reads)

Proposed changes

Apply to both registry/coder/modules/jfrog-token and registry/coder/modules/jfrog-oauth:

1. Extend the package_managers variable with a new optional pnpm list:

   pnpm = optional(list(string), [])

2. Reuse the existing .npmrc.tftpl template for pnpm (same registry + auth format). If both npm and pnpm are provided pointing to different repos, decide behavior: either (a) require they resolve to the same repo, or (b) generate a merged .npmrc with the pnpm entries scoped appropriately.
3. In run.sh, add a pnpm block mirroring the npm block:

   if [ -z "${HAS_PNPM}" ]; then
     not_configured pnpm
   else
     echo "📦 Configuring pnpm..."
     jf pnpmc --global --repo-resolve "${REPOSITORY_PNPM}"
     cat << EOF > ~/.npmrc
   ${NPMRC}
   EOF
     config_complete
   fi

   Note: verify the exact config subcommand name (jf pnpmc vs jf pnpm-config) against the shipped CLI.
4. Pass HAS_PNPM, REPOSITORY_PNPM into the templatefile(...) call in main.tf.
5. Update README.md examples to include pnpm = ["npm-local"] (or a dedicated repo) and show jf pnpm install <pkg> usage.
6. Add a pnpm case in *.tftest.hcl to assert the script contains the jf pnpmc invocation.
7. Bump module versions and note the new input in the changelog/README.

Notes / open questions

• pnpm uses the same npm-type Artifactory repo, so we may not need a separate variable — but a dedicated pnpm key keeps the UX consistent and future-proofs it if JFrog diverges.
• The module doesn't install pnpm itself (matches existing behavior for npm, go, etc.) — document this in the README.
• Confirm minimum jf CLI version we should recommend (>= 2.98.0 for pnpm 10.x, >= 2.116.0 for pnpm 11.x).

Created on behalf of @matifali

[linear-code]

ENG-3273