Fix the second Value() example in the manpage

[rawsun007]

Fixes #4499.

The second Value() example never ran its builder, for two reasons. Value(output) wraps the existing Value Node in a new Value Node instead of using it, so the builder would have written into a throwaway Node. And nothing depended on the target: the default target . only reaches filesystem Nodes, so a Value target on its own is never built. This change passes the Nodes directly and adds a second builder that writes the updated Value to output.txt, following the pattern in test/Value/Value.py. It also removes the TODO comment.

I copied the example block out of Environment.xml into an SConstruct and ran it with scripts/scons.py. output.txt contains after, a second run is up to date, and changing 'after' rebuilds it. bin/docs-validate.py passes.

Contributor Checklist:

• I have created a new test or updated the unit tests to cover the new/changed functionality.
• I have updated CHANGES.txt and RELEASE.txt (and read the README.rst).
• I have updated the appropriate documentation

No test was added, because this change only touches a manpage example. test/Value/Value.py already covers the same builder pattern.

Written by Claude Code (Claude Opus 5.5) under my account, as the Assisted-by: trailer says. It is a fix for the issue above, not something found by a code audit.

🤖 Generated with Claude Code

[mwichmann]

Thanks for pitching in. We have a fairly elaborate system for describing, and then running and capturing output from examples, with the idea they won't sit there broken - in the User Guide. That's not used in the manpage so there's a risk examples either don't work from the start, or "rot" so they stop working. Tried to validate some manual, thus the comment I left on that example. If it passes review, it will be nice to have that one working.