chore: rename project Roundtable → Steward

Renames the Python package directory, CLI command, env var prefix,
docker-compose service/container/image, Postgres role/db, and all
visible branding. Marketing form is "Fabled Steward".

Clean break from the previous rebrand: drops the fabledscryer→roundtable
import shim in __init__.py and the FABLEDSCRYER_* env var fallback in
config.py and migrations/env.py. Env vars are now STEWARD_* only.

Heads-up for existing deployments:
- Postgres user/db renamed fabledscryer → steward in docker-compose.yml.
  Existing volumes need the role/db renamed inside Postgres, or override
  POSTGRES_USER/POSTGRES_DB to keep the old names.
- Host-agent systemd unit is now steward-agent.service. Existing agents
  keep running under the old name; reinstall to switch.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

steward/core/plugin_index.py

@@ -0,0 +1,93 @@
+# steward/core/plugin_index.py
+"""Remote plugin catalog: fetch, parse, and cache the plugin index.yaml."""
+from __future__ import annotations
+import logging
+import time
+from typing import Any
+
+logger = logging.getLogger(__name__)
+
+_CACHE_TTL = 300  # seconds
+# Per-URL cache: url → (raw_data, fetched_at monotonic)
+_url_cache: dict[str, tuple[dict, float]] = {}
+
+
+class CatalogPlugin:
+    """One entry from the remote plugin index."""
+
+    __slots__ = (
+        "name", "version", "description", "author",
+        "min_app_version", "download_url", "checksum_sha256",
+        "repository_url", "homepage", "license", "tags",
+    )
+
+    def __init__(self, data: dict[str, Any]) -> None:
+        self.name: str = data.get("name", "")
+        self.version: str = data.get("version", "0.0.0")
+        self.description: str = data.get("description", "")
+        self.author: str = data.get("author", "")
+        self.min_app_version: str | None = data.get("min_app_version")
+        self.download_url: str = data.get("download_url", "")
+        self.checksum_sha256: str = data.get("checksum_sha256", "")
+        self.repository_url: str = data.get("repository_url", "")
+        self.homepage: str = data.get("homepage", "")
+        self.license: str = data.get("license", "")
+        self.tags: list[str] = data.get("tags", [])
+
+
+async def _fetch_one(url: str, force: bool = False) -> list[CatalogPlugin]:
+    """Fetch a single index URL, using per-URL cache."""
+    import httpx
+    import yaml
+
+    now = time.monotonic()
+    if not force and url in _url_cache:
+        raw, fetched_at = _url_cache[url]
+        if now - fetched_at < _CACHE_TTL:
+            return [CatalogPlugin(p) for p in raw.get("plugins", [])]
+
+    try:
+        async with httpx.AsyncClient(timeout=10) as client:
+            resp = await client.get(url)
+            resp.raise_for_status()
+        raw = yaml.safe_load(resp.text) or {}
+        _url_cache[url] = (raw, now)
+        logger.info("Plugin catalog fetched from %s: %d plugin(s)", url, len(raw.get("plugins", [])))
+        return [CatalogPlugin(p) for p in raw.get("plugins", [])]
+    except Exception:
+        logger.exception("Failed to fetch plugin catalog from %s", url)
+        if url in _url_cache:
+            raw, _ = _url_cache[url]
+            logger.warning("Returning stale cached catalog for %s", url)
+            return [CatalogPlugin(p) for p in raw.get("plugins", [])]
+        return []
+
+
+async def fetch_catalog(
+    index_urls: str | list[str],
+    force: bool = False,
+) -> list[CatalogPlugin]:
+    """Fetch and merge plugin catalogs from one or more index URLs.
+
+    Results are cached per-URL for _CACHE_TTL seconds. Plugins with the same
+    name across repos are deduplicated — the first occurrence (repo list order)
+    wins. Pass force=True to bypass all caches.
+    """
+    if isinstance(index_urls, str):
+        index_urls = [index_urls]
+
+    seen: dict[str, CatalogPlugin] = {}
+    for url in index_urls:
+        url = url.strip()
+        if not url:
+            continue
+        for plugin in await _fetch_one(url, force=force):
+            if plugin.name not in seen:
+                seen[plugin.name] = plugin
+
+    return list(seen.values())
+
+
+def clear_catalog_cache() -> None:
+    """Invalidate all in-process catalog caches."""
+    _url_cache.clear()