feat: add indexer-core skill with data modeling guidance

[Agilulfo1820]

Summary

• Adds a new references/data-modeling.md reference file to the indexer-core skill, documenting BigDecimal/DECIMAL128 patterns for monetary and large-number fields in indexer models
• Updates the SKILL.md reference table with a new row pointing to the data-modeling guide
• Covers model annotations, event param parsing, arithmetic, API serialization, and VersionedDocument compatibility

Test plan

• Verify the new reference file renders correctly on GitHub
• Verify the SKILL.md reference table link resolves to the new file
• Confirm no other skills were modified

🤖 Generated with Claude Code

[github-actions]

Skill Security Audit

Scanned 69 file(s) — found 14 issue(s) across 5 file(s).

🔵 LOW (14)

File	Line	Finding	Excerpt
skills/thor/references/contributing.md	6	External URL: golangci-lint.run	https://golangci-lint.run/usage/install/
skills/thor/references/contributing.md	261	External URL: golang.org	https://golang.org/doc/effective_go
skills/x-2-earn-apps/references/getting-started.md	153	External URL: image.png	https://image.png
skills/x-2-earn-apps/references/getting-started.md	153	External URL: twitter.com	https://twitter.com/tweet/1
skills/x-2-earn-apps/references/security.md	124	External URL: docs.guardianstack.ai	https://docs.guardianstack.ai/
skills/x-2-earn-apps/references/sustainability-proofs.md	16	External URL: image.png	https://image.png
skills/x-2-earn-apps/references/sustainability-proofs.md	17	External URL: twitter.com	https://twitter.com/tweet/1
skills/x-2-earn-apps/references/sustainability-proofs.md	33	External URL: twitter.com	https://twitter.com/tweet/123
skills/x-2-earn-apps/references/sustainability-proofs.md	106	External URL: link-to-proof.com	https://link-to-proof.com
skills/x-2-earn-apps/references/sustainability-proofs.md	106	External URL: link-to-image.com	https://link-to-image.com/1.png
skills/x-2-earn-apps/references/sustainability-proofs.md	192	External URL: link-to-proof.com	https://link-to-proof.com
skills/x-2-earn-apps/references/sustainability-proofs.md	192	External URL: link-to-image.com	https://link-to-image.com/1.png
skills/x-2-earn-apps/references/sustainability-proofs.md	255	External URL: x.com	https://x.com/user/status/123456
skills/x-2-earn-apps/references/vepassport.md	149	External URL: vechain-energy.github.io	https://vechain-energy.github.io/vebetterdao-signal-admin/

[github-actions]

Skill Size Report

Skill	SKILL.md (always loaded)	Ref files (on demand)	Total est. tokens	Alerts
thor	~1.3K tok	13 files, ~25.3K tok	~26.6K tok	✅
create-vechain-dapp	~1.8K tok	3 files, ~14.2K tok	~16.0K tok	⚠️ monorepo.md ~10.8K tok (consider splitting)
smart-contract-development	~1.1K tok	5 files, ~14.9K tok	~15.9K tok	⚠️ smart-contracts.md ~6.6K tok (consider splitting)
vechain-kit	~1.4K tok	7 files, ~13.0K tok	~14.4K tok	✅
x-2-earn-apps	~1.0K tok	6 files, ~10.0K tok	~11.1K tok	✅
vebetterdao	~918 tok	4 files, ~9.3K tok	~10.2K tok	✅
vechain-core	~1.2K tok	4 files, ~8.7K tok	~9.9K tok	✅
vechain-react-native-dev	~1.5K tok	3 files, ~6.7K tok	~8.2K tok	✅
stargate	~736 tok	2 files, ~5.0K tok	~5.7K tok	✅
indexer-core	~1.2K tok	5 files, ~3.0K tok	~4.1K tok	✅
frontend	~1.1K tok	1 files, ~3.0K tok	~4.0K tok	✅
auto-voting-relayers	~2.8K tok	0 files, ~0 tok	~2.8K tok	⚠️ SKILL.md ~2.8K tok (always in context)
secure-github-actions	~752 tok	1 files, ~754 tok	~1.5K tok	✅
translate	~1.2K tok	0 files, ~0 tok	~1.2K tok	✅
grill-me	~418 tok	0 files, ~0 tok	~418 tok	✅
TOTAL			~132.1K tok

Large reference files (>5.0K tok)

File	Est. tokens
create-vechain-dapp/references/monorepo.md	~10.8K
smart-contract-development/references/smart-contracts.md	~6.6K

How to read this: SKILL.md is always loaded into the context window. Reference files are loaded on demand when the topic matches. Token counts are estimates (~4 chars/token). Consider splitting reference files over ~5.0K tokens.