Refresh CONTRIBUTING testing section: vector TSVs are real now

The Testing strategy bullet list claimed loc-spec.tsv,
iso8601-2.tsv, and edge-cases.tsv were planned for a future
release. Those files shipped in e742539 and the test harness
exercises them on every run. Update the section to reflect the
actual state and to mention EdtfFormatterTest (added in 0a283cc).

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jeffreyameyer

CONTRIBUTING.md

@@ -117,24 +117,23 @@ Transifex rather than patching the file directly.
 ## Testing strategy
 
 - **Unit tests** per class (e.g., `EdtfDateTest`,
-  `L0ParserTest`, `L1ParserTest`, `L2ParserTest`).
+  `L0ParserTest`, `L1ParserTest`, `L2ParserTest`,
+  `EdtfFormatterTest`).
 - **Generated parity vectors** under
   `src/test/resources/vectors/{level0,level1,level2}.tsv`,
   produced by `scripts/generate-vectors.mjs` from the upstream
   edtf.js. `GeneratedVectorsTest` reads them and asserts that
   `Edtf.parse(...)` agrees with edtf.js on type, level, min, max,
   and round-trip rendering.
-- **Planned for a future release**:
-  - `loc-spec.tsv` — hand-curated rows from the
-    Library of Congress EDTF spec examples.
-  - `iso8601-2.tsv` — rows from the ISO 8601-2:2019 (and
-    Amendment 1, 2025) clause examples.
-  - `edge-cases.tsv` — worst-case Unicode, boundary, and
-    deliberately-invalid inputs.
-
-  These three are not in the repository yet; if you write any of
-  them, drop them in `src/test/resources/vectors/` and add a
-  matching `@TestFactory` method in `GeneratedVectorsTest`.
+- **Spec vectors**: `loc-spec.tsv` (Library of Congress EDTF
+  examples) and `iso8601-2.tsv` (ISO 8601-2:2019 standard
+  examples) under the same path, also driven by
+  `GeneratedVectorsTest` `@TestFactory` methods.
+- **Edge cases**: `edge-cases.tsv` — worst-case inputs with
+  a 7th `valid` column. INVALID rows assert
+  `EdtfParseException`; VALID rows round-trip. Add new
+  pathological inputs here as you find them; the harness picks
+  them up automatically on the next test run.
 
 ## Security