feat: the pipeline runs the schema check first

PR validation runs validate_schemas.py --source-only and the pipeline did not, so a profile with an unquoted numeric core name passed every step and failed CI on push. It is step 0 now, skipped where jsonschema is not installed.

wiki/adding-a-platform.md

@@ -365,6 +365,7 @@ python scripts/pipeline.py --offline
 
 This executes in sequence:
 
+0. `validate_schemas.py --source-only` - the schema check PR validation runs
 1. `generate_db.py` - rebuild `database.json` from `bios/`
 1b. `provenance_report.py` - dump-catalog coverage from `provenance/`
 2. `refresh_data_dirs.py` - update data directories (skipped with `--offline`)

wiki/tools.md

@@ -23,6 +23,7 @@ Pipeline steps:
 
 | Step | Description | Skipped by |
 |------|-------------|------------|
+| 0/8 | Validate profiles and platform YAMLs against the schemas | - (no `jsonschema` installed) |
 | 1/8 | Generate database | - |
 | 1b | Dump-catalog coverage report | - (offline, reads `provenance/`) |
 | 1c | Romset recipes: identify archives, list rebuild targets | - (offline, reads `recipes/`) |