fix(coverage): ignore case comments and done redirections (#634)

[Chemaclass]

Summary

• Case patterns with trailing comments (e.g. *thing) # note) were counted as executable lines.
• Loop terminators with redirections or pipes (done < file, done <<<"$var", done | sort, done < <(cmd)) were counted as executable lines.
• Both inflated the executable-lines denominator and distorted coverage percentages.

Fix

• src/coverage.sh::bashunit::coverage::is_executable_line:
  • Allow an optional trailing (#.*)? on the case-pattern regex so *pat) # comment is recognized as non-executable.
  • Add a new check that treats done followed by any of <, >, |, & as a non-executable loop terminator.

Test plan

• ./bashunit tests/unit/coverage_executable_test.sh tests/unit/coverage_core_test.sh
• ./bashunit tests/
• ./bashunit --parallel tests/
• make sa
• make lint
• New regression unit tests for each reported pattern
• Integration test via get_executable_lines on a fixture with all patterns

Closes #634