feat: add lsp_defs/refs to all schemas + Rust/Terraform presets

[jamestexas]

Summary

• Add lsp_defs (definitions) and lsp_refs (references) content sources to the lsp file_set across all language schemas, completing the LSP materialization story alongside existing hover and diagnostics
• Create Rust preset schema (10 construct types: functions, structs, enums, traits, implementations, type_aliases, constants, statics, modules, macros) with proper selectors including impl_item type: for impl blocks
• Create Terraform/HCL preset schema (7 construct types: resources, data, variables, outputs, modules, locals, providers) using #eq? predicates to distinguish block types
• Register both presets in sourceCodePresets and presetSchemas so auto-detection uses them instead of FCA inference
• Fix serve --schema to use resolveSchema() for preset name support (was calling os.ReadFile directly)

Test plan

• task test — all existing tests pass including TestResolveSchema_AllPresets (rust + terraform)
• TestSourceCodePresets_SubsetOfPresetSchemas validates all preset keys resolve
• E2E: mache serve on ley-line/rs with Rust preset — 791 functions, 52 structs, 15 enums, 2 traits, 50 implementations verified via MCP tools
• E2E: Terraform schema against real .tf files — validate #eq? predicates
• E2E: leyline lsp enrichment → verify definitions/references files materialize

🤖 Generated with Claude Code