feat: add dev build mode to npm publish workflow

[scotwells]

Summary

• Add release-mode input to publish-npm-package.yaml with two modes:
  • dev (default): publishes x.y.z-dev.{sha} to the dev npm dist-tag. No version bump commit, no git tag.
  • release: existing behavior — auto-bumps version from PR labels, creates git tag, publishes stable version to latest.
• Skip path filtering for release mode — releases are intentional and should always publish
• Document the workflow in CLAUDE.md with single-file caller example

Single workflow file for both modes

Callers use one workflow with a dynamic release-mode expression:

name: Publish Package
on:
  push:
    branches: [main]
  release:
    types: [published]

jobs:
  publish:
    uses: datum-cloud/actions/.github/workflows/publish-npm-package.yaml@v1
    with:
      package-name: "@datum-cloud/my-package"
      package-path: packages/my-package
      release-mode: ${{ github.event_name == 'release' && 'release' || 'dev' }}
    secrets: inherit

• Push to main → release-mode: dev → publishes 0.1.2-dev.abc1234 to dev tag
• GitHub release → release-mode: release → bumps version, publishes to latest tag

Backwards compatibility note

The default release-mode is dev. Existing callers that don't pass the input will switch from stable to dev builds. They need to either:

1. Add release-mode: release to keep current behavior, or
2. Adopt the single-file pattern above for both dev + release

Test plan

• Verify workflow YAML passes actionlint
• Test dev mode: push a change, confirm x.y.z-dev.{sha} published with dev tag
• Test release mode: create a GitHub release, confirm version bump + stable publish
• Verify release mode skips path filtering (always publishes)

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