When a story modifies existing files, create-story must read those
files before generating dev notes. Without this, dev agents improvise
design decisions without knowing the current state of the code, leading
to regressions caught only at review time.
Adds a step at the end of Step 3 (Architecture analysis) that reads
every file marked UPDATE in the architecture directory structure and
documents its current state, what the story changes, and what must
be preserved.
Fixes#2273
Co-authored-by: Brian Madison <bmadcode@gmail.com>