tui-react: add reusable pager support for long text output

Context

tui-react should have a reusable way to present long, mostly static text with familiar pager-style navigation instead of each CLI reinventing scroll behavior.

I looked into how gh handles this since it is a good reference point for terminal UX.

Prior art: GitHub CLI

GitHub CLI already treats paging as a reusable concern rather than something every command implements manually:

• supports GH_PAGER
• falls back to PAGER
• also has pager-related config / behavior in the CLI
• uses an external pager model instead of baking custom scrolling into every command

Related references from gh docs/issues:

• GH_PAGER, PAGER environment variable support
• pager support discussions/issues such as cli/cli#528, cli/cli#5101, cli/cli#3617

This seems like the right conceptual model here too.

Problem

Right now there does not seem to be a standard tui-react primitive/pattern for "show a lot of text and let the user move through it comfortably".

That leaves apps to choose between:

• dumping raw output to the terminal
• implementing custom scrolling/search/keybindings themselves
• building a whole full-screen TUI even when the need is just pager-style viewing

Proposal

Add reusable pager support to tui-react for long text output.

Possible directions:

1. External pager integration

   • respect GH_PAGER-style / PAGER-style env configuration
   • default to less when appropriate
   • hand off plain text/markdown output to the pager

2. Built-in pager component / mode

   • a lightweight pager view for long static content
   • scrolling, page up/down, quit, search hooks, and sane keybindings
   • usable without building a full custom screen manager

3. Abstraction layer

   • a common interface so apps can say "render this content in paged mode"
   • implementation can choose external pager vs in-app pager based on environment / interactivity

Why this matters

There are really two distinct UX patterns:

• paged output for long, mostly static text
• full-screen TUI for highly interactive applications

A library like tui-react seems like a good place to make that distinction explicit and reusable.

Desired outcome

Ideally app authors can do something like:

• render long help/docs/log/output through a standard pager API
• get familiar navigation behavior out of the box
• avoid implementing one-off scroll containers for every CLI

Notes

This is not necessarily asking for a full curses-style app framework feature. Even just establishing the recommended abstraction/pattern for pager support would be valuable.

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Filed by Molty on behalf of @schickling

No implementation files, entry points, or tests are named. Start by locating the tui-react package and its existing text-output or scrolling primitives, then review the GitHub CLI pager references described in the issue. Done should mean that the project has a decided, reusable pager API or pattern with documented navigation and environment behavior.