fix: apply --limit to the write, not to the selection

pull.py's docstring said "the limit is on the write, not on the
selection", and the code did the opposite: `list_issues` truncated the
payload list to `limit`, and pull.py dropped the closed ones after that.
A milestone whose first issues are closed therefore answered `--limit 20`
with twelve files, and the only statement about the behavior anywhere was
the false one.

The limit now counts what the run leaves in the store. `list_issues`
takes a `keep` predicate, pages keep arriving until `limit` payloads have
satisfied it, and the ones that did not are still returned — they were
enumerated, and pull.py still reports them as "N closed, not stored".
What `keep` means stays the caller's business; the transport only counts.
pull.py hands it `lands_in_store`, which is the same test the walk itself
applies: a closed issue counts only when the store already has it, since
that one is refreshed rather than dropped.

Pagination is the other half, and it cuts both ways. `paginate` is now a
thin wrapper over a new `pages` generator, so the page after the one that
fills the budget is never requested. In the other direction "fetch until
N are kept" is "fetch the whole tracker" on a filter that matches mostly
closed issues, so a keep-bounded read scans at most PAGE_SLACK times the
pages the limit would need if nothing were dropped, then warns on stderr
and returns short. Raising --limit raises that ceiling with it. --deps is
outside the count: a dependency is followed because an issue named it.

remote.py keeps the old meaning and now says so in as many words — it
writes nothing, so there is no write for a limit to bound, and its
--limit caps the listing, closed issues included. Same flag, two jobs,
documented in both scripts and in the skill's command table.

Also refuses `--limit 0` instead of dividing by the page size and
raising ZeroDivisionError.

tests/test_pull_limit.py stubs the transport with a fake that serves
`page=`/`limit=` itself, so the request pattern is observed rather than
assumed: exactly N files out of a half-closed selection, the second page
fetched and the third not, the scan stopping at the budget with a
warning, and remote.py's listing unchanged. 251 tests, no network.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

skills/sync/scripts/remote.py

@@ -16,6 +16,11 @@ Usage:
     remote.py [--state open|closed|all] [--label L]… [-q TEXT]
               [--milestone M] [--limit N] [--repo owner/repo]
 
+`--limit` here caps the LISTING: N lines out, closed ones among them. That is
+not what the same flag means to `pull.py`, and the difference is not an
+oversight — pull.py bounds what it writes, and this command writes nothing, so
+there is nothing else for a limit to bound. Enumeration is the whole job.
+
 Login: the operator's pin from .claude/settings.local.json (see /tea:auth).
 """
 import argparse