memory: snapshot — U5 released at v0.3.0, and the index goes two-tier

The two dated log sections had never been split, so every one of their 29
entries sat inline and the startup index had grown to 372 lines — which is
the cost the two-tier scheme exists to remove, paid on every session that
reads the file. 27 entries were over threshold. All 29 now have a detail
file under persistent-memory.d/ and a one-line index entry that routes
rather than restates. Index: 372 -> 93 lines.

No archival. The soft cap fired, but every entry in this repo is dated
2026-09-21 or later, so the under-14-days guard held all of them back — and
the split alone took the index well under the target without moving
anything out of the active file.

The in-flight section is rewritten for the post-release state: nothing is
in flight, no gate is outstanding, and the next unit is explicitly recorded
as the operator's undecided call rather than as a plan. The session's
recommendation (U4, on three grounds) is written down so it does not have
to be re-derived, alongside the two alternatives and why they are
alternatives.

Two dated predictions are carried forward with their dates and their
instruments: the U5 adoption re-measure on 2026-09-29, which already reads
3 of 24 announced and 2 with a why from peers told nothing, and the
.forever re-count a fortnight AFTER U4 lands, which is U4's own success
criterion and is destroyed by running it early.

persistent-memory.d/2026-09-21-extracted-from-eshpfi.md

@@ -0,0 +1,7 @@
+# Extracted from `eshpfi` into its own repo
+
+_2026-09-21 · booth_
+
+**Extracted from `eshpfi` into its own repo.** The accreted
+service came over whole, tests included, so `tests/test_booth.py` (1581 lines)
+is the regression net the v1 rewrite is checked against.