fix: preserve continuation-line glossary definitions

[arunimshukla]

Summary

parseGlossary() only reads definition text from the glossary term line. In the current map content, Data Availability Layer (DA Layer) places its definition on the immediately following line, so the generated entry contains an empty definition and is omitted from the public glossary.

This change:

• reads the immediate next line when the inline definition is empty
• refuses to consume a category heading or another glossary term
• preserves existing single-line and linked-term parsing
• regenerates src/data/glossary.json with the missing DA Layer definition

The earlier glossary-link work from #45 is now present on main through commit 63f99bd. This is an independent follow-up based on that commit.

Reproduction

Against current main:

• the graph build reports 74 glossary terms
• Data Availability Layer (DA Layer) is generated with "definition": ""

After this patch, the term count remains 74 and the source definition is preserved.

Regression coverage

The tests cover:

• a definition on the immediate continuation line
• a missing definition followed by another term
• a missing definition followed by another category
• existing linked-term and inline-definition behaviour

Validation

• npm test: 61/61 passed
• npm run lint:refs: passed
• npm run build: passed, 218 pages built