fix(ci): update 3 doc references to tooling/schema_version.py

asset-pipeline.md (2 locations) and systems-schema.sql still pointed
at import_economics.py as the SCHEMA_VERSION home after the extraction
to a shared module.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/data/systems-schema.sql

@@ -485,7 +485,7 @@ CREATE INDEX IF NOT EXISTS idx_gate_links_to ON gate_links(to_system_id);
 -- One row per generator, updated on each successful non-dry-run.
 -- schema_version: monotonic semver string (e.g. "1.0.0") — bump on backwards-incompatible changes.
 --                 Orderable, enabling savegame migration lineage (Phase 5+).
---                 Defined as SCHEMA_VERSION constant in tooling/economy-db/import_economics.py.
+--                 Defined as SCHEMA_VERSION constant in tooling/schema_version.py.
 -- schema_sha:     SHA-1 hex of systems-schema.sql content at generation time (tamper detection).
 -- generator_sha:  SHA-1 hex of the generator source file(s) content
 -- generated_at:   ISO-8601 UTC timestamp of the run