Nested task-body `Requires` clauses
A Requires clause written as a bullet in a task's body is now recognized.
Previously only inline clauses and plain continuation clauses were scanned, so
a clause in a body bullet was silently ignored during renumbering and
dangling-dependency validation. Two faults followed from that silence, and both
are fixed:
- Insertion could re-point a consumer. Inserting before a prerequisite renumbered the consumer to the anchor the prerequisite vacated, so a clause that was never scanned kept its old text and the consumer ended up depending on whichever unrelated item inherited that number. A rewritten clause now names its prerequisite's own new anchor.
- Deletion could produce a self-dependency. Deleting a still-required prerequisite left the surviving consumer naming the anchor the deleted item used to hold, which now resolved to the consumer itself. In in-place mode that invalid result was written to disk.
Upgrading may surface new failures. An edit that would strand a surviving
consumer is now rejected with a dangling-dependency error before anything is
written, and in in-place mode the original file is left byte-identical. A
delete or replace that previously appeared to succeed while writing an
invalid roadmap will now fail instead. The failure is the correct outcome — the
roadmap it used to write did not satisfy its own Requires clauses — but a
script that ignored the exit status and relied on the write will need updating.
No other behaviour changes. Section references such as §2.1, version numbers,
ordered-list numbering, and fenced code examples keep their bytes.