docs: record Ε-W3 as landed and Phase Ε as complete

docs/COMPLETED.md

@@ -1039,5 +1039,39 @@ genuine folder-name collision (`sanitizeRenameCount` vs `collisionRenameCount`)
 a hostile or foreign-spelled entry name (e.g. an unexpected extension) always
 lands sanitized rather than verbatim.
 
-**Ε-W3 (`package-compat-fixtures`) has not landed** and is the only remaining
-wave of Phase Ε.
+### Ε-W3 — The compatibility fixtures
+
+The phase's third and final wave, and with it Phase Ε's implementation is complete: the
+version-compatibility policy stated in `docs/product/bank-package.md` is now a property
+proven against frozen bytes rather than an assertion in a doc.
+
+**Ε-W3-T1 — `package-compat-fixtures`.** A new checked-in corpus of 23 frozen `.rsbank`
+fixtures under `tests/fixtures/package_compat/` — one v1 package written by the shipping
+build (`1.4.0`), a synthetic additive-forward package (`formatVersion` 2 /
+`minReaderVersion` 1) carrying three keys this build has never heard of, a synthetic
+structural-refusal package (2/2), nine truncations (one per distinct decode failure
+site, including one cut at `additive_forward.rsbank`'s own payload boundary), and eleven
+hostile-name packages (six bad entry names, five bad nested `relativePath` values) —
+every payload a single 300-byte 16-bit mono WAV, ~15 KB for the whole corpus. Two new
+test targets decode and exercise it: `package_compat_tests` (frozen bytes decode to
+exactly what the shipping build wrote, the additive fixture reads with every unknown key
+skipped, every truncation classifies `Malformed` and never `TooNew`, every hostile name
+is refused before any planner runs) and `package_round_trip_tests` (the same corpus
+driven through the actual verbs — export → import → export over `v1_shipping.rsbank`
+yields byte-identical payloads, and every refusal fixture refuses the whole import with
+nothing landed and nothing in the index). A new repo-root `.gitattributes` (`*.rsbank
+binary`) is load-bearing, not decoration: under `core.autocrlf = true`, git's NUL-sniffing
+heuristic would text-classify a future short, ASCII-heavy fixture and CRLF-mangle it on a
+Windows checkout, silently breaking the frozen-bytes premise the whole corpus rests on. A
+standalone DAW verification script, `docs/verify-package-transfer.md`, covers the one
+claim no unit test can make — a real cross-machine transfer, including the too-new
+refusal, the truncated-download refusal, and mid-payload corruption, each read off as an
+exact message string. **Open question resolved:** the recommendation (one-sample
+packages, a few hundred bytes of payload each) was followed — the corpus holds
+one-sample packages with a 300-byte payload each. **Deviation from spec:** the plan
+called for a truncation cut mid-layout; RSBK stores no layout section (the layout is
+derived from the manifest's entries, not stored as its own section), so the fixture that
+exercises "the manifest parses, the layout computes, the exact-size proof fails" lands at
+the payload boundary instead. No production module was touched — the wave adds test-tree
+files, the corpus, its README, the verification script, and one path variable in the root
+`CMakeLists.txt`.

docs/PLAN.md

@@ -2404,6 +2404,9 @@ import gate can key on `LedgerStatus` alone without going through `pruneDryRun()
 enumeration+scan). **No Ε track touches `core/instrument/`, `shell/instrument/`, or any
 capture backend.**
 
+**All three waves have landed — Phase Ε is complete.** W1 through W3 each carry their own
+landed note below; see `docs/COMPLETED.md` for every track's full narrative.
+
 ---
 
 ### Ε-W1 — The contract, the filesystem, and the ledger's new kind
@@ -2568,52 +2571,17 @@ against a package this build is incapable of writing.
 **One track.** The whole deliverable is one corpus and the harness over it; splitting it
 would mean two tracks writing two halves of one fixture set.
 
-#### Ε-W3-T1 — `package-compat-fixtures`
-
-**Goal.** Turn the version-compatibility policy from an assertion in a doc into a property
-proven against **frozen bytes**, so a later format change cannot silently break either
-direction.
-
-**Spec:** `docs/product/bank-package.md` §"Version tagging: both directions".
-
-**Surface boundary — owns:** a new checked-in fixture corpus under the package modules' test
-tree, the harness that decodes it, and one `docs/` verification script for the DAW half.
-**Does not own:** any production module — if a fixture reveals a defect, the fix is filed
-against the owning track's module and this track carries the failing test, not the patch.
-
-**Behavior.**
-- **Frozen bytes, not regenerated ones.** The corpus holds real `.rsbank` bytes committed to
-  the repo: a v1 package written by the shipping build, a synthetic
-  `formatVersion` = N+1 / `minReaderVersion` = current package (the additive-forward case),
-  and a synthetic `formatVersion` = N+1 / `minReaderVersion` = N+1 package (the refuse case).
-  A test that regenerates its own fixture proves only that the code agrees with itself —
-  which is precisely the failure mode a format ladder exists to catch.
-- **A truncation corpus.** The valid package truncated at a spread of offsets, each asserted
-  `Malformed` rather than `TooNew`, so the two recoveries never get crossed.
-- **A hostile-name corpus.** Packages whose entry names carry `..`, separators, and absolute
-  prefixes, each refused.
-- **The round-trip anchor.** Export → import → export over the v1 fixture yields
-  byte-identical payloads.
-- **A standalone DAW verification script** in `docs/`, following the
-  `docs/verify-track-scope-multitrack.md` precedent — the cross-machine transfer is the one
-  claim no unit test can make.
-- **The corpus is append-only.** When a future format version ships, its fixture is added;
-  no existing fixture is ever regenerated or edited. Stated in the corpus's own README so the
-  rule survives the person who wrote it.
-
-**Acceptance criteria.**
-- All three version fixtures classify as specified, and the additive-forward one imports with
-  every known field intact and every unknown key skipped.
-- Every truncation offset classifies `Malformed`; none classifies `TooNew`, `Readable`, or
-  crashes.
-- Every hostile-name fixture is refused at decode, before any planner runs.
-- The round-trip fixture's payloads are byte-identical after export → import → export.
-- The DAW script exists and names its steps concretely enough to run without reading this
-  plan.
-
-**Open questions.** **[propose at review]** how large the committed corpus is allowed to be —
-the recommendation is one-sample packages with a few hundred bytes of payload each, since the
-properties under test are structural and a large payload proves nothing extra.
+**Ε-W3-T1 has landed** — `package-compat-fixtures` — see `docs/COMPLETED.md` for the full
+narrative. 23 frozen `.rsbank` fixtures now live under `tests/fixtures/package_compat/`
+(three version fixtures, nine truncations, eleven hostile-name packages, ~15 KB total),
+decoded by a new `package_compat_tests` and driven through export → import → export by a
+new `package_round_trip_tests`, plus the DAW script `docs/verify-package-transfer.md` for
+the one claim no unit test can make. A repo-root `.gitattributes` (`*.rsbank binary`)
+keeps the frozen bytes frozen under `core.autocrlf`. No production module was touched.
+**Open question resolved:** the recommendation was followed — the corpus is one-sample
+packages with a 300-byte payload each. **Deviation from spec:** RSBK stores no layout
+section (it is derived from the manifest), so the planned "mid-layout" truncation lands
+at the payload boundary instead, where the manifest parses but the exact-size proof fails.
 
 ---