refactor: harden codebase and remove unicode artifacts

- fix urllib.parse.quote import (was urllib.request.quote)
- add operator precedence parens in generate_pack dedup check
- narrow bare except to specific types in batocera target scraper
- cache load_platform_config and build_zip_contents_index results
- add selective algorithm support to compute_hashes
- atomic write for fetch_large_file (tmp + rename)
- add response size limit to base scraper fetch
- extract build_target_cores_cache to common.py (dedup verify/pack)
- hoist _build_supplemental_index out of per-platform loop
- migrate function-attribute caches to module-level dicts
- add @abstractmethod to BaseTargetScraper.fetch_targets
- remove backward-compat re-exports from common.py
- replace em-dashes and unicode arrows with ASCII equivalents
- remove decorative section dividers and obvious comments

scripts/scraper/retrodeck_scraper.py

@@ -171,7 +171,7 @@ def _resolve_path(p: str) -> str:
 def _extract_bios_entries(component_val: dict) -> list[dict]:
     """Extract BIOS entries from all three possible locations in a component.
 
-    No dedup here — dedup is done in fetch_requirements() with full
+    No dedup here -dedup is done in fetch_requirements() with full
     (system, filename) key to avoid dropping valid same-filename entries
     across different systems.
     """
@@ -338,13 +338,13 @@ class Scraper(BaseScraper):
                     if resolved.startswith("saves"):
                         continue
 
-                    # Build destination — default to bios/ if no path specified
+                    # Build destination -default to bios/ if no path specified
                     if resolved:
                         destination = f"{resolved}/{filename}"
                     else:
                         destination = f"bios/{filename}"
 
-                    # MD5 handling — sanitize upstream errors
+                    # MD5 handling -sanitize upstream errors
                     md5_raw = entry.get("md5", "")
                     if isinstance(md5_raw, list):
                         parts = [str(m).strip().lower() for m in md5_raw if m]