bootstrap.sh wrote .diachron-version to the temp clone directory
instead of the target project, causing upgrade.sh to fail. Fix that
and teach all three scripts (bootstrap, upgrade, diff-upstream) about
the new ? prefix convention in file-list.
Sample files (?-prefixed) are copied on bootstrap but left alone on
upgrade so user modifications are preserved. New samples introduced
in a newer framework version are still copied if absent.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
New script extracts a diff of framework files against the upstream
ref in .diachron-version. Both DIACHRON.md and diachron/AGENTS.md
now explain how to use it and recommend keeping framework changes
in discrete, well-described commits to ease upstreaming.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
