docs: document http_get_contains validator and public localhost UI li…

[Derssa]

Summary of Changes

This PR updates the roadmap authoring documentation file (docs/roadmap-format.md) to align with the newly implemented HTTP validation features.

Key additions:

• Documents the http_get_contains validator type and its parameter schema (node, port, path, expectedText).
• Adds a "UI Integrations & Localhost Access" section detailing how the frontend automatically surfaces clickable localhost links for web server containers when correct networking preconditions (liveness, public subnets, and port 80 security rules) are met.

Types of Changes

• New feature / node type addition
• Bug fix (non-breaking change resolving an issue)
• Refactoring / structural cleanup
• Documentation update

Verification & Testing

Automated Checks

• Run npm run lint successfully with no errors
• Run npm run build successfully with no compilation errors
• Run npm test successfully (all tests pass)

Manual Verification

• Verified the markdown syntax renders cleanly and the reference tables align correctly.

Checklist

• My code follows the repository's code style and lint standards
• I have updated the documentation or instructions if necessary
• All unit and integration tests are passing