docs(spec): the liveness README's author-warning section states the verdict model the lint ships

A dead, live-elsewhere or experimental ledger row warns its author on its
own; authorWarn only opts a planned row in. Every warning shows the row's
authorHint or the verdict's default hint, never the note. Rule 1 is restated
for the verdict, rule 2 for any materialized schema default, and the
coverage paragraph names the walk's real reach. Two sentences elsewhere in
the README that tied a dead row's warning to authorWarn are corrected.

Claude-Session: https://claude.ai/code/session_01UtnxvdiN376GF3sgXwAw4d
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

.changeset/21135-liveness-readme-author-warnings.md

@@ -0,0 +1,15 @@
+---
+"@objectstack/spec": patch
+---
+
+Liveness ledger README: the "Author warnings" section now describes the model the liveness lint ships. A `dead`, `live-elsewhere` or `experimental` verdict warns on its own, and `authorWarn` only opts a `planned` row in.
+
+Clause-②: no
+
+- The section said warnings were opt-in per ledger row, and that only `experimental` warned without the marker. That stopped being true when the lint made a `dead` or `live-elsewhere` verdict warn on its own. The section now has one table of which verdicts warn, and under which rule id.
+- `authorHint` no longer "falls back to `note`". Every warning shows the row's `authorHint`, or else the verdict's default hint. The `note` never reaches an author.
+- Rule 1 now talks about the verdict, not the marker. Grading a row `dead`, `live-elsewhere` or `experimental` warns every author who sets the key, and fails their `os lint --strict` / `os validate --strict` run. No marker keeps it quiet, so a benign display key is measured against the designer-previews ruling before it is graded `dead`.
+- Rule 2 (booleans) now covers any key whose schema default materializes. It no longer points at an `_authorWarnSkipped` marker, which no ledger carries.
+- The coverage paragraph states the walk's real reach: the types it visits, one level of `children`, and that a governed type it does not visit warns no author through this lint.
+- Two sentences elsewhere in the README said a `dead` row needs `authorWarn` to warn. Both are corrected the same way.
+- ⛔ Documentation only: no ledger row, schema, export or lint behaviour changes.