[cschanhniem]

Implements I6 from NEXT_100_PR_MAP: versioned schema export.

What

• schema_export.py: SEM- manifest for schema discovery by partner tools
• SchemaExportEntry: 7 fields (schema_name, schema_path, schema_id, version, stability_tier, description, is_dry_lab_only)
• SchemaExportManifest: entry list + tier counts + is_stable_export flag
• VALID_STABILITY_TIERS: {stable, experimental, internal, deprecated}
• validate_schema_export_manifest(): 10 rules (prefix, tier vocab, duplicate names, is_stable_export consistency)
• format_schema_export_manifest(): tier-marked listing with [+]/[~]/[.]/[!] symbols
• 63 tests across 5 test classes
• BASELINE: 7906 to 7969

Why

Partners need to know which schemas are stable and at what version. The SEM- manifest gives them a machine-readable discovery document.

Disconfirming pass

• No existing schemas modified; new export layer only
• is_dry_lab_only=True default enforced
• No safety/calibration policy changed