Fix cargo-llvm-cov HTML generation conflict in CI

[RAprogramm]

Problem

After merging #216, the generate-coverage job fails in CI because we're running two conflicting cargo-llvm-cov commands:

1. cargo llvm-cov nextest --profile ci --lcov - generates coverage with nextest
2. cargo llvm-cov --html - tries to generate HTML by re-running coverage WITHOUT nextest

This causes the second command to fail.

Solution

Remove HTML coverage report generation from CI workflow. The HTML report is only needed for local development, not in CI. Codecov provides its own web interface for coverage visualization.

Changes:

• Remove "Generate HTML coverage report" step from generate-coverage job
• Remove target/llvm-cov/html/ from artifact upload path
• Update summary message

Related

• Related to Fix Codecov unknown coverage and test analytics configuration #213, Enhance codecov.yml with component management and flags #215
• Caused by workflow reorganization in PR 215 #216

Test Plan

• CI should complete successfully on main after this fix
• Coverage data should upload correctly to Codecov