Probed after 1.3.0 landed, on advisor challenge. Both came back clean --
these pin them so they cannot regress silently.
1. A `- ` item whose text begins with a YAML indicator AND carries a `": "`
could in principle route into the block-mapping path with a
half-validated key instead of into `_reject_dangerous_value`. It does
not: `&anchor id` fails `_KEY_RE` on the key side, so the item falls
through intact and raises on the indicator. One row each for & * ! %
backtick, plus the merge key inside an entry.
2. `_consume_block_mapping` ends at a blank line and at column zero, and
hands an index back to `_consume_block_list`, which hands one back to
`_parse_flat`. A line orphaned by that boundary -- a `resource:` left
over from a mapping that closed early -- must RAISE, not be dropped. A
pointer that vanishes rather than failing is this repo's failure class,
so it gets a test rather than a probe. Plus the return-index contract:
a top-level key after a multi-entry list is neither swallowed nor
re-read as an item.
868 green (was 859), 130/130 classes. Test-only; no source change.