Qualify “source” as convention source or module source

The unqualified term “source” refers both to reusable convention providers and to TypeScript import/export module specifiers, with additional generic source identifiers in the parser. This makes types, variables, messages, and documentation ambiguous.

Relevant files:

• packages/konsistent/src/config/source-resolver.ts
• packages/konsistent/src/config/reference-expander.ts
• packages/konsistent/src/typescript/types.ts
• packages/konsistent/src/typescript/predicates/import-source.ts
• docs/reference/reusable-conventions.md

Use the fully qualified terms “convention source” and “module source” throughout code and prose, including identifiers such as conventionSourceMap and moduleSource. Avoid bare source wherever either domain meaning is possible.

Backward compatibility: internal names and documentation can be renamed or removed without compatibility shims. No konsistent.json schema change is required; if a schema-facing field is renamed, retain the old name and behavior as deprecated and emit a non-failing CLI warning when it is used.