fix: remove entity type overlaps causing causality region conflicts

[hudsonhrh]

Summary

• Four file/ipfs data source templates declared entity types (Task, Project, Proposal, DDVProposal, EducationModule) they never write to — but that ARE written by onchain ethereum event handlers in the same block
• In specVersion 1.2.0, file data sources run in a separate offchain causality region. When their entities list overlaps with onchain handler entity types, the store detects causality region conflicts during block transaction commit
• This caused non-deterministic "WASM runtime thread terminated" / "Failed to transact block operations" crashes — the failure point shifted each retry because IPFS fetch order varies
• Fix: restrict each file data source's entities list to only the metadata entity type the handler actually writes to

Why previous fixes didn't work

• PR fix: resolve causality region conflict crashing indexer #161 (handler causality fix) and fix: rewrite ProposalMetadata handler to prevent immutable entity INSERT conflicts #162 (immutable entity pattern) fixed real issues but didn't address the yaml-level entity overlap
• PR fix: add missing duplicate checks to all IPFS data source callers #163 (duplicate data source checks) added good defensive checks, but the Graph node already prevents duplicate runtime hosts (the warnings), so the root cause was elsewhere
• The key evidence: non-deterministic failure point + 5 WASM threads killed simultaneously pointed to a block-transaction-level conflict, not a handler-level bug

Test plan

• npm run codegen passes
• npm run build passes
• All 241 tests pass
• subgraph-lint passes (0 errors)
• Redeploy and verify indexing past the previously failing block

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