docs: ratify the carrier endgame terminal classes

docs/test-system-v2.md

@@ -52,6 +52,34 @@ sweep spans lib test fixtures, import probes, and a zero-dep root-only
 build; the former 815/940/951 driver-parity carriers were folded into it,
 their content identity already owned by their corpus twins.
 
+## Carrier endgame
+
+The declarative corpus and the native `@test` owners are the permanent
+test surface — the `go/test/` analogy. The native C carrier fleet is the
+pre-Go-1.5 artifact and shrinks toward exactly two terminal classes:
+
+1. **C-bootstrap observers.** The five in-process units watch the C
+   frontend from inside its own process and are irreplaceable while
+   `cmd/` is the live frontend. The six bootstrap gates are the same
+   class's proof column: they compare the wwstage tools against the C
+   stage to a fixed point. At the eventual selfhost flip both freeze
+   into a bootstrap smoke gate (Go 1.5 deleted its C toolchain and that
+   toolchain's tests; it did not port them).
+2. **Host ABI/platform gates.** Behavior owned by the host linker,
+   loader, or ABI (`996_dyn_ww` today). These observe the platform, not
+   the compiler, and stay native exactly as long as the claim is about
+   the platform.
+
+Everything else gets a ww owner. Byte and artifact observations —
+assembly-pattern greps, symbol tables, frame layouts, `.wwi`
+round-trips, driver-leg comparisons — are subprocess plus file IO plus
+string search, which `test/package/package_test.ww` already performs
+natively (runcommand + in-language assertions). A C carrier whose
+assertions fit that shape is ported and retired in the same commit,
+assertions preserved or strengthened, with no compatibility execution
+path left behind. A carrier that is merely historical is deleted
+outright; git history is the archive.
+
 ## Public targets
 
 | Target | Composition |