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.

tests/test_compat.py

@@ -23,6 +23,7 @@ import pytest
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "tools"))
 
 import compat  # noqa: E402
+import compat_publish  # noqa: E402
 from compat import (  # noqa: E402
     NESTED,
     PROVIDERS,
@@ -574,3 +575,57 @@ class TestATransientNetworkBlipDoesNotWakeAnybody:
             "def get_restic_config(entry, credentials):\n    pass\n"
         )
         assert compat.fingerprint(self._rows(worse)) != compat.fingerprint(self._rows(broken))
+
+
+class TestTheBotFindsItsOwnIssueOnBOTHForges:
+    """`find_issue` decides "have I already filed this?" -- and it ran on two forges.
+
+    It used to skip pull requests with `"pull_request" not in i`. GitHub omits that key
+    on a plain issue; **Gitea sends it as `null`**. So on Gitea every issue looked like
+    a PR, the match list was always empty, and the bot took the "nothing filed yet"
+    branch on EVERY run: nine duplicate copies of the same report on the canonical
+    forge, four of them filed after the commit that was supposed to stop exactly this.
+
+    It is the same failure the spam fix was written to prevent, moved from comments to
+    issues -- and it survived because `find_issue` was the one function here with no
+    test. So the payload shapes are pinned, per forge, by hand.
+    """
+
+    TITLE = compat_publish.TITLE
+
+    def _find(self, monkeypatch, payload):
+        monkeypatch.setattr(compat_publish, "_call", lambda *a, **k: payload)
+        return compat_publish.find_issue("https://forge/api", "tok", self.TITLE)
+
+    def test_gitea_sends_pull_request_as_null_and_the_issue_is_still_found(self, monkeypatch):
+        found = self._find(monkeypatch, [
+            {"number": 7, "title": self.TITLE, "state": "open", "pull_request": None},
+            {"number": 1, "title": self.TITLE, "state": "open", "pull_request": None},
+        ])
+        assert found is not None, (
+            "find_issue missed a Gitea issue, so the bot files a NEW duplicate report "
+            "every run -- which is how nine of them piled up"
+        )
+        assert found["number"] == 1, "lowest-numbered wins"
+
+    def test_github_omits_the_key_entirely_and_the_issue_is_still_found(self, monkeypatch):
+        found = self._find(monkeypatch, [
+            {"number": 2, "title": self.TITLE, "state": "open"},
+        ])
+        assert found is not None and found["number"] == 2
+
+    def test_a_real_PR_with_the_same_title_is_still_skipped_on_both(self, monkeypatch):
+        # The reason the filter exists at all: both forges list PRs on /issues, and
+        # commenting on a PR instead of the bug report would be worse than useless.
+        assert self._find(monkeypatch, [
+            {"number": 3, "title": self.TITLE, "state": "open",           # Gitea PR
+             "pull_request": {"merged": False}},
+            {"number": 4, "title": self.TITLE, "state": "open",           # GitHub PR
+             "pull_request": {"url": "https://api.github.com/..."}},
+        ]) is None
+
+    def test_an_unrelated_issue_is_not_mistaken_for_the_report(self, monkeypatch):
+        assert self._find(monkeypatch, [
+            {"number": 1, "title": "TypeError when create B2 backup on Electric Eel",
+             "state": "closed", "pull_request": None},
+        ]) is None