feat: add build logs viewing for Xcode Cloud actions

[Claude]

Implements artifact-based log viewing for completed build actions, similar to GitHub Actions and CircleCI workflows.

Changes

API Client (src/lib/appstoreconnect/client.ts)

• Added downloadArtifactContent(downloadUrl) method to fetch log content from Apple's artifact URLs

Command Implementation (src/extension.ts)

• Implemented xcodecloud.viewBuildLogs command with artifact discovery and download
• Created dedicated "Xcode Cloud Logs" output channel for log display
• Added file size formatting helper for human-readable artifact sizes
• Filters artifacts by fileType: 'log' or filename pattern matching

UI Integration (package.json)

• Added context menu entries for buildAction and buildActionTest nodes
• Command appears in action group alongside trigger/cancel operations

Usage

Right-click any completed build action → "View Build Logs". Logs display in the output panel with:

• Multi-artifact support (e.g., build-log, test-log)
• File sizes and download status
• Clear error messaging for unavailable logs (pending/skipped/expired)

API Flow

getBuildActionArtifacts(actionId) 
  → filter for log artifacts 
  → getArtifact(artifactId) for download URL 
  → downloadArtifactContent(url) 
  → display in output channel

Logs are unavailable for running/pending actions and are subject to Apple's retention policies.