Available disk space per tablespace

Solai's testing report on v5 — no new technical substance

A new participant (Solai, solai.cdac@gmail.com) posted a brief testing confirmation of v5 on Linux. The message reports:

• Clean apply and build
• pg_tablespace_avail() returns values matching df -h
• \db+ shows the new "Free" column
• Custom tablespace and non-superuser access work correctly
• make check TESTS=tablespace passes

This is a straightforward +1/works-for-me report with no new technical analysis, no code review findings, and no engagement with the open issues from Parragi's review (overflow bug, Windows error handling, documentation wording). It does not advance the thread toward resolving any of the outstanding v6-required items.

Berg has still not responded to Parragi's review.