Adds skills/story-lifecycle/SKILL.md, a community skill inspired by
the BMAD Method's epic/story/sprint workflow: a self-contained,
file-based delivery loop (Epic → Stories → Sprint → Implement → Done)
with all state under .stories/, no external PM tool required.
Rebuilt on current upstream/main as a skill-only diff, per affaan-m's
review (same blockers as #2309): the shared format-code.ts Windows fix
and github-coordination branch-coverage tests that were bundled here
now live in #2459. Skill count recomputed as 277->278 against current
main (the old bump was stale, which was the actual conflict source).
Also repoints the Related Skills entry from the closed project-context
skill (#2310) to dev-team, which now owns reading/generating
PROJECT-CONTEXT.md.