docs(u5): state what the contract deliberately leaves out

The out-of-scope block is load-bearing for the cross-frontier review
gates — without negative constraints their signal-to-noise drops sharply,
and both /heid-code-review and /heid-bug-hunt refuse to fire without one.
Written for the reviewer, but it is the same list the roadmap gate
produced: the what-landed feed is parked for v1.1, nothing enforces that
a booth must announce itself (rsync is a documented path and never runs
the CLI), and the manifest describes rather than decides — U4 owns
lifetime.

docs/contracts/u5_booth_manifest.contract.md

@@ -224,6 +224,26 @@ guarded with an explicit `{% if %}` rather than relying on `b.manifest.handle`
 rendering as Undefined, because the two lanes' cards differ and a silent
 Undefined in one of them is how the kept lane would quietly keep the old defect.
 
+## Out of scope
+
+Deliberately deferred or never. Divergence here is not drift.
+
+- **A second index ordering keyed on `created`** — a "what landed" feed. Operator
+  decision, 2026-09-22: parked for v1.1. It is a new ordered collection needing
+  its own stated rule, it competes with the existing order for what "the third
+  one" means, and it has nothing to sort the 26 manifest-less booths by.
+- **`why` in the zip manifest, or a `booth ls` column.** One-liners over the
+  same record, neither on the v1 path.
+- **Enforcing that a booth MUST announce itself.** `rsync` is the documented
+  path for every host that is not nh3-dev and never runs the CLI, so a refusal
+  would break the documented workflow. The marker is the whole mechanism.
+- **Deleting, expiring or migrating anything based on the manifest.** U4 owns
+  lifetime; this unit only describes.
+- **Any change to how items, marks, blur, keep or the link board work.** The
+  manifest is a dotfile and every existing listing already skips it.
+- **Auth, or treating a manifest as trusted.** Standing non-goal; the Booth is
+  LAN-internal and a hand-written `.booth.json` is a supported input.
+
 ## Invariants
 
 **INV-1 — one resolver for the manifest.** `read_manifest(booth)` is the only