feat: show load_from, built_by and pin fields

load_from, found_by, on_mismatch, built_by, pin_frozen and
version_source were in the profiles and on no page: Dolphin's
gba_bios.bin showed a path under system/ although the libretro core reads
it from its save directory, and mame0278 did not say only Recalbox ships
it.

tests/test_site_emulator_page.py

@@ -0,0 +1,73 @@
+"""What an emulator page says about a profile and its files.
+
+No network and no database: pages are rendered from small profiles.
+"""
+
+from __future__ import annotations
+
+import sys
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(REPO_ROOT / "scripts"))
+
+import generate_site as gs  # noqa: E402
+
+EMPTY_DB = {"files": {}, "indexes": {"by_name": {}}}
+
+
+def _page(name: str, profile: dict) -> str:
+    return gs.generate_emulator_page(name, profile, EMPTY_DB, None, set())
+
+
+class WhereAndHowAFileIsRead(unittest.TestCase):
+    """load_from, found_by and on_mismatch were in 99, 4 and 25 entries and
+    on no page: Dolphin's gba_bios.bin showed a Path a RetroArch user put
+    under system/, while the libretro core reads it from its save directory."""
+
+    def test_load_from(self):
+        page = _page("dolphin", {"type": "standalone + libretro", "files": [
+            {"name": "gba_bios.bin", "path": "GBA/gba_bios.bin",
+             "load_from": {"libretro": "save_dir"}},
+            {"name": "hdd.rom", "load_from": "hdd_image"},
+            {"name": "bios.bin", "load_from": "system_dir"},
+        ]})
+        self.assertIn("- Read from: the save directory, not the BIOS directory "
+                      "(libretro build)", page)
+        self.assertIn("- Read from: inside the emulated hard disk image", page)
+        self.assertEqual(page.count("Read from:"), 2)
+
+    def test_found_by_and_on_mismatch(self):
+        page = _page("x", {"type": "standalone", "found_by": "content", "files": [
+            {"name": "scph5501.bin", "found_by": "content", "on_mismatch": "warn"},
+            {"name": "boot.bin", "on_mismatch": {"signature": "warn"}},
+        ]})
+        self.assertIn("| Files found by | content (the code scans the folder", page)
+        self.assertIn("- Found by: content (", page)
+        self.assertIn("- On a failed check: warns and runs with the file", page)
+        self.assertIn("- On a failed signature check: warns and runs with the file", page)
+
+
+class WhoShipsTheBuildAndWhy(unittest.TestCase):
+    """built_by, pin_frozen and version_source were in 9, 13 and 40 profiles
+    and on no page: mame0278 did not say only Recalbox ships it."""
+
+    def test_meta_rows(self):
+        page = _page("mame0278", {
+            "type": "libretro", "built_by": ["recalbox"],
+            "pin_frozen": "ROCKNIX 20261001 builds this revision.",
+            "version_source": {"url": "https://example.org/news", "pattern": "v(\\S+)",
+                               "no_genuine_copy": "13.0"},
+            "files": [],
+        })
+        self.assertIn("| Built by | [recalbox](../platforms/recalbox.md), under its "
+                      "core name.", page)
+        self.assertIn("| Revision held | ROCKNIX 20261001 builds this revision. |", page)
+        self.assertIn("| Releases announced at | [https://example.org/news]"
+                      "(https://example.org/news) (version 13.0 announced there, "
+                      "found only as rebuilt copies) |", page)
+
+
+if __name__ == "__main__":
+    unittest.main()