Document list and git helper call-site behavior

[codeforester]

Summary

• document that list_remove removes every exact match in one call
• document BASE_GIT_PULL_MAX_ATTEMPTS in the git_update_repo call-site comment

Fixes #110

Review notes

• cleanup path accumulation was reviewed as non-actionable for now: eager cleanup removes temp files, and the exit dispatcher skips missing registered paths
• eager git log removal remains intentional so logs do not linger until shell exit

Validation

• rg -n "Removes every exact match" lib/bash/list/lib_list.sh
• sed -n '136,147p' lib/bash/git/lib_git.sh | rg -n "Environment|BASE_GIT_PULL_MAX_ATTEMPTS"
• ./tests/validate.sh
• git diff --check