v0.31.0: meta-only repository topology (ROADMAP #36)

Retire the per-RFC-repo model. RFCs now live in their meta-repo entry
(rfcs/<slug>.md) for their whole life; graduation is an in-place
super-draft → active state flip that keeps the body in the entry — no
repo creation, no body-strip, no five-step transaction, no rollback.

SPEC: §1 topology rewritten (one meta/content repository, no per-RFC
repos) with a deployer-facing "single content repository" framing; §2
(repo: always-null), §3 (active is in-place), §4, §9.8 (handoff
frictions dissolve), and §13 fully rewritten (two-field dialog, "The
flip", §13.6 RFC-0001 fold-back record).

Code: graduation collapses to open+merge one frontmatter PR; branch/PR/
chat dispatch re-keyed on meta-residency (repo IS NULL) so active RFCs
edit on the meta repo exactly as super-drafts do; the two "RFC has no
repo" 409 guards removed; promote-to-branch slug-embeds an active RFC's
auto-branch (edit-<slug>-<hex>) for shared-repo cache attribution;
refresh_meta_branches + hygiene branch-resolution include meta-resident
actives; the §9.8 read-only guard + pre_graduation_history scoped to
legacy per-repo only; dead bot primitives + GraduateDialog repo field +
blocking-PR popover removed. The repo: frontmatter field and the
/blocking-prs endpoint are retained (schema stability / informational).

Tests: graduation suite rewritten to the flip model; e2e + hygiene
updated. Full backend suite 375 passed; frontend builds.

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

backend/app/cache.py

@@ -342,9 +342,13 @@ async def refresh_meta_branches(config: Config, gitea: Gitea) -> None:
         if not slug:
             continue
         rfc = db.conn().execute(
-            "SELECT state FROM cached_rfcs WHERE slug = ?", (slug,)
+            "SELECT state, repo FROM cached_rfcs WHERE slug = ?", (slug,)
         ).fetchone()
-        if not rfc or rfc["state"] != "super-draft":
+        # Meta-only topology (§1): edit branches live on the meta repo for
+        # every meta-resident entry — super-drafts and active RFCs alike
+        # (active RFCs are graduated in place and keep editing here, §13).
+        # A legacy per-RFC repo (repo set) is the only thing excluded.
+        if not rfc or rfc["repo"] or rfc["state"] not in ("super-draft", "active"):
             continue
         edit_keys_seen.add((slug, name))
         db.conn().execute(
@@ -365,7 +369,8 @@ async def refresh_meta_branches(config: Config, gitea: Gitea) -> None:
     # diverges from this single point.
     if meta_main_sha:
         super_drafts = db.conn().execute(
-            "SELECT slug FROM cached_rfcs WHERE state = 'super-draft'"
+            "SELECT slug FROM cached_rfcs "
+            "WHERE repo IS NULL AND state IN ('super-draft', 'active')"
         ).fetchall()
         for r in super_drafts:
             db.conn().execute(
@@ -387,7 +392,8 @@ async def refresh_meta_branches(config: Config, gitea: Gitea) -> None:
         SELECT b.rfc_slug, b.branch_name
           FROM cached_branches b
           JOIN cached_rfcs r ON r.slug = b.rfc_slug
-         WHERE r.state = 'super-draft'
+         WHERE r.repo IS NULL
+           AND r.state IN ('super-draft', 'active')
            AND b.state != 'deleted'
            AND b.branch_name != 'main'
         """