v0.30.1: fix phantom pending-idea after merge-with-branch-delete

refresh_meta_pulls / refresh_rfc_repo recover a PR's slug from its
Gitea head.ref, which collapses to the refs/pull/<N>/head sentinel
once a merged PR's branch is deleted. The slug then parsed to None,
the row was skipped, and cached_prs.state froze at 'open' — so the
entry showed as both a super-draft and a pending idea. Recover the
real branch name from the stored cached_prs row when Gitea reports an
empty or sentinel ref.

Surfaced via the ROADMAP #35 operator authoring lane (CLI merge with
--delete-branch); the web UX leaves branches in place so it never hit
this. Regression test added; full suite 375 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/tests/test_propose_vertical.py

@@ -577,6 +577,97 @@ def test_propose_to_super_draft_vertical(app_with_fake_gitea):
         assert ("merge_proposal", "ben") in kinds
 
 
+def test_merged_idea_pr_with_deleted_branch_clears_proposal(app_with_fake_gitea):
+    """Regression: a merged idea PR whose branch was deleted must not
+    linger as a 'pending idea' ghost.
+
+    Found via the ROADMAP #35 operator authoring lane: merging an idea
+    PR from the CLI with `--delete-branch` makes Gitea report the PR's
+    `head.ref` as the synthetic `refs/pull/<N>/head` sentinel instead of
+    `propose/<slug>`. `refresh_meta_pulls` derives the slug from the
+    branch name, so the sentinel parsed to slug=None, the row was skipped,
+    and `cached_prs.state` stayed frozen at 'open' — leaving the entry
+    showing as BOTH a super-draft (cached_rfcs reconciled off the push)
+    AND a pending idea (cached_prs never updated). The fix recovers the
+    original branch name from the already-stored cached_prs row.
+
+    The web UX never tripped this because it leaves the branch in place
+    (the repo's default_delete_branch_after_merge is false).
+
+    The bug only manifests on an out-of-band merge (the PR merged +
+    branch deleted directly in Gitea, with the in-app merge endpoint never
+    reconciling the row while the branch still existed) -- which is exactly
+    what the #35 CLI lane does. An in-app merge reconciles cached_prs to
+    'merged' before the branch is gone, so it never trips this; the test
+    therefore drives the Gitea state directly to reproduce the CLI path.
+    """
+    from fastapi.testclient import TestClient
+    from app import db, cache, gitea as gitea_mod
+    from app.config import load_config
+
+    app, fake = app_with_fake_gitea
+
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor", email="alice@test")
+        r = client.post("/api/rfcs/propose", json={
+            "title": "Informed Consent",
+            "slug": "informed-consent",
+            "pitch": "A first-class definition of consent in OHM.",
+            "tags": [],
+        })
+        assert r.status_code == 200, r.text
+        pr_number = r.json()["pr_number"]
+
+        # The proposal is cached as an open idea PR.
+        items = client.get("/api/proposals").json()["items"]
+        assert any(i["pr_number"] == pr_number for i in items)
+
+        # Out-of-band CLI merge (ROADMAP #35 lane): the PR is merged AND
+        # its branch deleted directly in Gitea, WITHOUT the in-app merge
+        # endpoint ever running. So cached_prs still says state='open' and
+        # Gitea now reports the merged PR's head.ref as the sentinel. This
+        # is the exact state `rfc-authoring.sh pr-merge --delete-branch`
+        # leaves behind.
+        for pr in fake.pulls[("wiggleverse", "meta")]:
+            if pr["number"] == pr_number:
+                # land the file on main (the push side already reconciles
+                # cached_rfcs into a super-draft via the webhook/sweep)
+                for (o, rp, br, p), data in list(fake.files.items()):
+                    if (o, rp, br) == ("wiggleverse", "meta", "propose/informed-consent"):
+                        fake.files[("wiggleverse", "meta", "main", p)] = dict(data)
+                pr["state"] = "closed"
+                pr["merged"] = True
+                pr["merged_at"] = "2026-05-29T12:13:00Z"
+                pr["closed_at"] = "2026-05-29T12:13:00Z"
+                pr["merge_commit_sha"] = fake._next_sha()
+                pr["head"]["ref"] = f"refs/pull/{pr_number}/head"
+        fake.branches[("wiggleverse", "meta")].pop("propose/informed-consent", None)
+
+        # The reconcile sweep runs (a later webhook, or the 5-min safety net).
+        import asyncio
+        cfg = load_config()
+        gclient = gitea_mod.Gitea(cfg)
+        asyncio.run(cache.refresh_meta_repo(cfg, gclient))
+        asyncio.run(cache.refresh_meta_pulls(cfg, gclient))
+
+        # The bug: this used to still list informed-consent (frozen 'open'
+        # row, slug unparseable from the sentinel). The fix recovers the
+        # stored branch name, so the row reconciles to merged and the ghost
+        # is gone.
+        assert client.get("/api/proposals").json()["items"] == []
+
+        # And the cached_prs row is correctly merged, not a frozen 'open'.
+        row = db.conn().execute(
+            "SELECT state FROM cached_prs WHERE pr_number = ?", (pr_number,)
+        ).fetchone()
+        assert row["state"] == "merged", f"expected merged, got {row['state']}"
+
+        # The super-draft itself is unaffected — still in the catalog.
+        items = client.get("/api/rfcs").json()["items"]
+        assert any(i["slug"] == "informed-consent" and i["state"] == "super-draft" for i in items)
+
+
 def test_slug_uniqueness_enforced(app_with_fake_gitea):
     from fastapi.testclient import TestClient
     app, _fake = app_with_fake_gitea