Respect PAGER, LESS, and NO_PAGER for response paging

[ryanfowler]

Summary

• Use $PAGER when paging response output instead of hard-coding less
• Honor NO_PAGER to disable the default auto pager
• Let $LESS control fallback less flags when $PAGER is unset
• Update terminal tests and docs to cover the pager precedence and fallback behavior

Testing

• cargo fmt
• cargo clippy --locked --all-targets --all-features -- -D warnings
• cargo test --all-features
• cargo test --all-features --test cli --test formatting --test grpc --test http --test network --test terminal --test update --test websocket -- --test-threads=1