docs: describe the v2 test architecture

test-system-v2.md is the authoritative owner table and target graph;
CLAUDE.md rule 13 moves from the sizelint gate to authoritative layout
helpers and rule 14 names the new targets; PROJECT_PLAN.md is marked
historical where superseded.

PROJECT_PLAN.md

@@ -1,5 +1,11 @@
 # WW Project Continuation Plan
 
+> Historical implementation log. The active test targets and ownership model
+> are documented in `docs/test-system-v2.md`. References below to `test/run`,
+> `test-run`, phase scheduling, last-green caching, frozen `internal/wwtest`,
+> or the 106-fixture prototype describe superseded 2026-08-05 states; they are
+> retained only as dated design history and are not current operator guidance.
+
 Status date: 2026-08-05
 
 Canonical baseline: `master` at `3d7973596422f1c9e2275016a5f264a2ae504ceb`
@@ -393,22 +399,34 @@ Remaining:
 
 ### 5.4 Package-driver limitations
 
-- `ww test DIR` discovers only immediate `_test.ww` files and does not recurse.
-- Files are not sorted deterministically.
-- Each discovered file is built separately instead of assembling one package
-  test unit. Same-package helper sharing therefore does not work as expected.
-- Production enumeration excludes all `*test.ww`, while test discovery includes
-  only `_test.ww`; the naming rules disagree.
-- Only the first glob argument reaches the runner even though the runner can
+This list records the pre-T1 audit baseline. The 2026-08-05 single-directory
+vertical slice closes deterministic sorting, compatible group assembly,
+multiple-filter forwarding, no-test/no-match behavior, dependency-test
+exclusion, and deterministic `-c` output. Recursive discovery and package
+`-o` remain deliberately outside that slice.
+
+- `ww test DIR` discovered only immediate `_test.ww` files and did not recurse.
+- Files were not sorted deterministically.
+- Each discovered file was built separately instead of assembling one package
+  test unit, so same-package helper sharing did not work as expected.
+- Production enumeration excluded all `*test.ww`, while test discovery included
+  only `_test.ww`; the naming rules disagreed.
+- Only the first glob argument reached the runner even though the runner could
   support more than one.
-- A single file with no tests can silently return success, while a directory
-  with no recognized tests can error. Define one consistent contract.
-- Imported dependency tests are stripped. This is normally correct, but root
-  package files containing tests must be assembled into the root test build.
-- `-c` without `-o` can leave a temporary test executable behind.
+- A single file with no tests could silently return success, while a directory
+  with no recognized tests could error.
+- Imported dependency tests were stripped correctly, but root package files
+  containing tests were not assembled into the root test build.
+- `-c` without `-o` could leave a temporary test executable behind.
 
 ### 5.5 Runner-protocol limitations
 
+This list likewise records the pre-slice audit baseline. The first package
+vertical slice closes completion proof, failure clamping, timeout/group cleanup,
+skip reasons, expected-abort state, and qualified current-test identity. The
+remaining invalid-attribute diagnostics and abort/exit-1 ABI ambiguity are
+tracked in the later task sections.
+
 - A test can call `os.exit(0)` before completing and the parent reports it as a
   pass. The parent needs an explicit completion token from the child.
 - The runner returns the raw number of failures. At 256 failures, the Unix exit
@@ -622,6 +640,16 @@ before declaring all of T0 complete.
 
 ### T1: Implement package-aware `ww test`
 
+First vertical slice status (2026-08-05): one explicit immediate directory is
+planned in byte order; production and same-package tests share a white-box
+binary; the exact `<package>_test` group uses a second binary; imported tests do
+not leak; qualified IDs, multiple filters, explicit empty outcomes, direct
+per-test supervision, completion proof, timeout cleanup, and exit clamping are
+covered natively. Both public drivers delegate to the same package planner but
+pass their own compiler stage. Recursive `./...`, package concurrency/caching,
+package `-o`, universal filename migration, and the remaining attribute-shape
+diagnostics are still open, so T1 as a whole is not marked complete.
+
 - Introduce a package test-plan data structure in the driver.
 - Unify production-file exclusion and candidate discovery on `*_test.ww`, then
   classify candidates by their package declarations.