Patch: migrate-detection floor. /espalier-migrate's version detection
probes grep historical phrases, and later releases retire phrases — v0.22.1
replaced the comment-brevity line, v0.23.0 folded the speculative dispatch,
v0.25.0 rewrote pipeline.md and the lane SKILLs and moved the reviewer's
abuse-coverage step into a mode file — so a CURRENT install failed OLD
probes: on a v0.25.0 install the skill reported v0.13.1, v0.17.0, v0.21.1,
and v0.22.0 as needed, and those scripts would have re-inserted retired
text. Detection now ends with a supersession floor: the newest release
whose distinctive markers are present (modes/ + stages/ + the router
naming them for v0.25.0; the simplify SKILL + Simplification Review for
v0.24.0; Class Sweep; the Stage 5/6 fold; the no-comment default; the
dep-audit cache) forces every flag below it to no — an install carrying
a later release reached it through the chain or a fresh init, and the
floor release's own script stays re-runnable. Skill-only: no install file
changes, no migration script, nothing to run on an existing install. Test
35 gains three assertions that run the skill's detection block as-is
against a fresh v0.25.0 install, a real v0.24.0 install before migration
(only v0.25.0 flagged), and the same install after migration ("Already
fully up to date").