feat: add knulli, amberelec and emuelec platforms

Each OS publishes Batocera's systems dict (knulli-systems, and
batocera-systems at AmberELEC's newest prerelease commit and EmuELEC v4.8),
read with the shared parser. Cores come from each OS's own ES list.
AmberELEC and EmuELEC declare neogeo/ and ports/ beside bios/ from
/storage/roms, so their packs extract there and core_destination puts
core files under bios/.

scripts/scraper/knulli_scraper.py

@@ -0,0 +1,127 @@
+#!/usr/bin/env python3
+"""Scraper for KNULLI's knulli-systems.
+
+Source: package/system/knulli-scripts/scripts/knulli-systems
+Format: Python source, Batocera's `systems` dict, parsed by batocera_scraper
+Hash: MD5
+
+`msx1` and `msx2+` are written twice in the dict. Python keeps the later
+value of a repeated key when the script runs, and so does the parser.
+
+Verification (knulli-systems at the release tag):
+- checkBios (lines 867-927): md5sum() of the file at /userdata/<file>
+  against the declared md5, an empty md5 meaning presence only. For a
+  zippedFile entry, checkInsideZip() (lines 814-845) matches the member name
+  with casefold() and hashes it. A system or file carrying `emulator` and
+  `core` is checked only when es_systems.cfg offers that pair (coreExists,
+  lines 847-865).
+- Run by EmulationStation's BIOS screen (knulli-cfw/batocera-emulationstation
+  10834d00, es-app/src/ApiSystem.cpp:764-774) and by knulli-support:69.
+
+es_systems.yml and configgen-defaults.yml have Batocera's shape, so the cores
+are read with Batocera's code. The configgen generators do not: the hatari,
+melonds and gsplus generators and libretroOptions.py are older forms than the
+ones batocera_launchers reads, so no launcher layer is written.
+"""
+
+from __future__ import annotations
+
+import re
+import urllib.error
+import urllib.request
+
+from .base_scraper import BaseScraper, BiosRequirement, fetch_github_latest_version
+from .batocera_scraper import (
+    SYSTEM_SLUG_MAP as BATOCERA_SLUGS,
+)
+from .batocera_scraper import (
+    _not_cores,
+    configgen_cores,
+    extract_systems_dict,
+    platform_systems,
+    requirements_from_systems,
+)
+
+PLATFORM_NAME = "knulli"
+
+REPO = "knulli-cfw/knulli-linux"
+_RAW = "https://raw.githubusercontent.com/knulli-cfw/knulli-linux/{ref}/"
+SOURCE_TEMPLATE = _RAW + "package/system/knulli-scripts/scripts/knulli-systems"
+CONFIGGEN_DEFAULTS_TEMPLATE = (
+    _RAW + "package/system/knulli-configgen/configs/configgen-defaults.yml"
+)
+ES_SYSTEMS_TEMPLATE = _RAW + "package/emulationstation/knulli-es-system/es_systems.yml"
+
+# Batocera's names, plus the keys KNULLI writes that Batocera does not,
+# filed under the slug the other scrapers already give them. msu-md holds the
+# Mega-CD BIOS files Batocera files under megadrive-msu.
+SYSTEM_SLUG_MAP = {
+    **BATOCERA_SLUGS,
+    "o2em": "magnavox-odyssey2",
+    "msu-md": "sega-mega-cd",
+    "xbox": "microsoft-xbox",
+}
+
+
+class Scraper(BaseScraper):
+    """Scraper for KNULLI's knulli-systems."""
+
+    def __init__(self, url: str | None = None) -> None:
+        self.tag = "" if url else fetch_github_latest_version(REPO)
+        super().__init__(url=url or SOURCE_TEMPLATE.format(ref=self.tag))
+
+    def _fetch_text(self, url: str) -> str:
+        req = urllib.request.Request(url, headers={"User-Agent": "retrobios-scraper/1.0"})
+        try:
+            with urllib.request.urlopen(req, timeout=30) as resp:
+                return resp.read().decode("utf-8")
+        except urllib.error.URLError as e:
+            raise ConnectionError(f"Failed to fetch {url}: {e}") from e
+
+    def validate_format(self, raw_data: str) -> bool:
+        has_dict = re.search(r"^systems\s*=\s*\{", raw_data, re.MULTILINE) is not None
+        return has_dict and "def checkBios" in raw_data and '"biosFiles"' in raw_data
+
+    def fetch_requirements(self) -> list[BiosRequirement]:
+        raw = self._fetch_raw()
+        if not self.validate_format(raw):
+            raise ValueError("knulli-systems format validation failed")
+        return requirements_from_systems(extract_systems_dict(raw), SYSTEM_SLUG_MAP)
+
+    def generate_platform_yaml(self) -> dict:
+        systems = platform_systems(
+            self.fetch_requirements(), extract_systems_dict(self._fetch_raw()), SYSTEM_SLUG_MAP
+        )
+        # es_systems.yml files machine selectors and plugins under an
+        # emulator as Batocera's does: Batocera's list of them applies.
+        cores, standalone, dual = configgen_cores(
+            self._fetch_text(CONFIGGEN_DEFAULTS_TEMPLATE.format(ref=self.tag)),
+            self._fetch_text(ES_SYSTEMS_TEMPLATE.format(ref=self.tag)),
+            _not_cores("batocera"),
+        )
+        result = {
+            "platform": "KNULLI",
+            "version": self.tag,
+            "homepage": "https://knulli.org",
+            "source": self.url,
+            "base_destination": "bios",
+            "hash_type": "md5",
+            "verification_mode": "md5",
+            "cores": cores,
+            "systems": systems,
+        }
+        if standalone:
+            result["standalone_cores"] = standalone
+        if dual:
+            result["dual_mode_cores"] = dual
+        return result
+
+
+def main() -> None:
+    from .base_scraper import scraper_cli
+
+    scraper_cli(Scraper, "Scrape KNULLI BIOS requirements")
+
+
+if __name__ == "__main__":
+    main()