Split monolithic solana-dev skill into modular skills

[ArvinFarrelP]

This PR splits the monolithic solana-dev skill into multiple modular skills.

New skills:

• solana-anchor
• solana-pinocchio
• solana-client
• solana-testing
• solana-security
• solana-payments

Changes:

• Introduced skills/ directory with individual SKILL.md files
• Moved shared documentation to references/
• Updated README to reflect modular structure
• Updated install.sh to install all skills and shared references

This reduces context size and improves context isolation when invoking skills.

Closes #43

[lgalabru]

Thanks for jumping on this @ArvinFarrelP.

We should first get to the bottom of this issue (discussed here).

I think the proposed approach introduces a substantial devex regression.

[ArvinFarrelP]

Thanks for the feedback!

My goal with this PR was mainly to prototype the modular structure so we could evaluate the trade-offs more concretely.

If the concern is mainly around developer experience and installation flow, we could potentially keep a default solana-dev skill that bundles everything, while also exposing optional specialized skills for more focused contexts.

Happy to adjust the approach based on what direction you think fits the project best.