Release Collector: Consolidate meta-release viewers into single parameterized viewer

[hdamker]

Problem description

The Release Collector currently generates separate HTML viewer files for each meta-release (fall24.html, spring25.html, fall25.html). This creates maintenance overhead:

1. The REQUIRED_FILES array in release-collector-production.yml must be manually updated when adding new meta-releases
2. Multiple nearly-identical HTML files to maintain
3. Wiki embedding requires different URLs for each meta-release

Possible evolution

Replace the dedicated meta-release viewers with a single parameterized viewer that accepts the meta-release as a URL parameter:

• Single file: viewers/meta-release.html
• URL parameter: ?meta-release=Spring25
• Filter logic applied on page load based on parameter
• Validate parameter against known meta-releases from embedded config
• Show selector or error message if parameter missing/invalid

Benefits:

• Fixed set of deployment files (meta-release.html + portfolio.html)
• No workflow updates needed when adding new meta-releases
• Single codebase to maintain and enhance
• meta-release-mappings.yaml becomes single source of truth

Alternative solution

Derive REQUIRED_FILES dynamically from config/meta-release-mappings.yaml during validation. This keeps separate files but removes manual updates. Less elegant but lower implementation effort.

Additional context

Related to PR #98 review comment about hardcoded REQUIRED_FILES. The parameterized viewer approach aligns with the goal of reducing per-meta-release maintenance tasks.