feat: add API versioning, mobile responsive layout, and component tests

[tmushayahama]

Issues
#1

Changes

API Versioning (pango-toolbar)

• New apiVersion prop ('pango-1' | 'pango-2', default pango-2) for switching between v1/v2 configurations
• Auto-detects ?apiVersion= from URL when api-version attribute is not set
• Download links now use version-aware URLs via getConfig()

Environment Constants (environment.ts)

• Refactored from flat ENVIRONMENT object to BASE_CONFIG + VERSION_CONFIGS keyed by version
• Renamed constants from camelCase to SCREAMING_CASE to align with site-react
• V1 download paths include /v1/ segment; V2 ontology URL updated
• Added version metadata: APP_VERSION, GO_RELEASE, PANTHER_VERSION

Mobile Responsive Layout

• Toolbar actions now visible on all viewport sizes (previously hidden below 768px)
• Below 768px: icon-only buttons for Download, About, Help, and a logos dropdown
• Above 768px: unchanged desktop layout with text buttons and side-by-side logos

Dropdown Enhancements (pango-dropdown)

• New align prop ('left' | 'right') for dropdown positioning
• New --pango-dropdown-trigger-padding CSS variable

Tests

• 11 spec tests for pango-toolbar (default rendering, custom props, download links, V1/V2 URLs, partner logos)
• 10 spec tests for pango-dropdown (rendering, toggle, events, alignment)
• 6 e2e tests each for both components
• Image mock setup in stencil.config.ts for Jest PNG handling

CI/CD & Release Workflow

• Configured semantic-release for automated versioning, changelogs, npm publish, and GitHub releases
• Removed redundant publish.yml workflow
• Updated ci.yml to PR-only trigger (semantic-release handles push-to-main)
• Updated semantic-release.yml with explicit permissions and v24
• Added commitlint CI workflow for conventional commit enforcement
• Fixed package.json repository URL to pantherdb/pango-toolbar

Documentation

• Expanded README with contributing guide, conventional commit reference, and release workflow docs

Test plan

• Spec tests pass locally (25/25)
• CI build and test pass on PR
• After squash merge: semantic-release publishes 0.1.0 to npm
• After squash merge: GitHub release v0.1.0 created with auto-generated notes

cc @mugitty @dustine32