docs(ENG-238): Add algorithm registry and CPI linking

[alnoki]

Changes

1. Add algorithms/registry.json as a central declarative
   mapping between algorithm specs (.tex) and their assembly
   implementations (.s), replacing the scattered tex/asm
   prop pairs in markdown files and absorbing syscalls.json
2. Add cpis section to the registry for cross-program
   invocation targets with links to upstream source definitions
3. Simplify <Algorithm> component to a single id prop that
   resolves both the .tex source and assembly file from the
   registry
4. Extend .tex syntax to annotate CPI targets on syscalls
   (e.g. \CALL{sol-invoke-signed-c}{system-program::CreateAccount}),
   rendered as linked sol_invoke_signed_c(system_program::CreateAccount)
5. Add root prop to <AlgorithmIndex> for scoped dependency
   graphs showing only a single algorithm and its transitive deps
6. Switch dependency chart to LR layout with color-coded nodes
   (green algorithms, grey syscalls, blue CPIs)
7. Add build-time validation that every .tex file has a
   registry entry and vice versa
8. Fix prelude comment indentation in pseudocode rendering
9. Update docs-engine.md and CLAUDE.md documentation

[linear]

ENG-238