The bug-report bot re-filed itself every run on Gitea; nine copies

`find_issue()` skipped pull requests by testing for the PRESENCE of the
`pull_request` key. GitHub omits that key on a plain issue. Gitea sends it as
`null`. So on Gitea every issue was thrown away as if it were a PR, the lookup
came back empty on every run, and the bot took the "nothing filed yet" branch and
opened a brand-new report instead of editing the one already open.

Nine of them piled up on the canonical forge. Four were filed AFTER the commit
that was supposed to stop exactly this -- the same failure it was written to
prevent, moved from comments to issues. It survived because `find_issue` was the
one function here with no test; the mirror deduped correctly, and the mirror is
what anybody would have looked at.

Test the value, not the key: it is the only form that is true on both forges.
Pinned by tests that carry each forge's payload shape by hand.

Also send both paging parameters. GitHub reads `per_page`, Gitea reads `limit`,
and each ignores the other's; Gitea's default page is 30, so the lookup would
have begun missing the report once the pile it was creating outgrew one page.

tools/compat_publish.py

@@ -69,11 +69,18 @@ def find_issue(api, token, title):
     existed once (an earlier version put the ref list in the title, so the identity
     changed whenever that set changed), and an order-dependent pick would alternate
     between them -- reopening one while commenting on the other.
+
+    Both forges list PRs alongside issues, but they SAY SO DIFFERENTLY: GitHub omits
+    the `pull_request` key on a plain issue, Gitea sends it as `null`. Testing for the
+    KEY therefore discards every Gitea issue as if it were a PR -- so this returned
+    None on every Gitea run, and the bot filed a brand-new duplicate report each time
+    instead of editing the one it already had. Test the VALUE; it is the only form
+    that is true on both.
     """
-    issues = _call(f"{api}/issues?state=all&per_page=100", token)
+    issues = _call(f"{api}/issues?state=all&per_page=100&limit=100", token)
     mine = [
         i for i in issues
-        if i.get("title") == title and "pull_request" not in i   # GitHub lists PRs here
+        if i.get("title") == title and not i.get("pull_request")
     ]
     return min(mine, key=lambda i: i["number"]) if mine else None