fix: keep auto colors when paging is forced

[tianrking]

Summary

• preserve automatic ANSI color output whenever bat is going to launch a pager
• add a regression test for forced paging when stdout is not detected as a terminal

Root cause

--color=auto only consulted the original stdout handle. On Windows, that handle can be reported as non-interactive before bat replaces it with an external or built-in pager, so paging succeeded but syntax highlighting was disabled.

Validation

• cargo test --bin bat app::tests::auto_color_is_enabled_when_paging_is_forced_without_a_terminal -- --exact
• cargo fmt --check
• cargo clippy --bin bat --tests -- -D warnings
• git diff --check

Fixes #3833

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 77f1a42604

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Keep forced-pager output out of loop-through mode

When stdout is not a terminal and --paging=always is used with the default --color=auto, this sets colored_output to true, but loop_through just below still remains true because it only considers interactive_output, --color=always, --decorations=always, --force-colorization, or -n. In Controller::print_input, loop_through selects SimplePrinter, which copies bytes without syntax highlighting, so bat --paging=always file.rs from a non-TTY still feeds uncolored text to the pager despite this branch. The same forced-paging predicate needs to participate in the loop-through decision.

Useful? React with 👍 / 👎.