[Docs]: Reorganize skill categories for clarity and consistency

[rosspeili]

What needs to be fixed?

What needs to be fixed?

The current skill category structure is inconsistent and does not reflect the nature of the skills accurately. This issue proposes a reorganization of the category taxonomy used in the registry, documentation, and directory structure.

Problems with the current state

• The data_engineering category name is verbose and inconsistent with the shorter naming convention used elsewhere. It should be renamed to data.
• finance/wallet_screening is a compliance and risk assessment tool, not a general finance skill. It belongs in a compliance or security category.
• Category names are not consistently applied across the directory structure, manifest.yaml files, documentation, and the skills index.
• There is no documented rationale or guide for how categories are chosen when a new skill is contributed.

Proposed changes

• Rename data_engineering to data across the directory, manifests, and documentation.
• Move finance/wallet_screening to compliance/wallet_screening and update all references accordingly (manifest, docs, examples, tests, CI).
• Review all existing skills and ensure their category assignment is accurate. Document the criteria for each category in CONTRIBUTING.md.
• Add a category reference table to docs/skills/README.md describing what each category covers and which skills belong to it.

Affected files

• skills/data_engineering/ (rename to skills/data/)
• skills/finance/wallet_screening/ (move to skills/compliance/wallet_screening/)
• All manifest.yaml files for moved skills
• docs/skills/README.md
• docs/skills/wallet_screening.md
• CONTRIBUTING.md
• Any CI or test paths referencing the old paths

Acceptance criteria

• No skill lives under an incorrect or legacy category name.
• All tests, imports, and documentation reflect the updated paths.
• CONTRIBUTING.md documents how to choose a category for a new skill.
• CI passes cleanly after the rename.

Affected Page

• skills/data_engineering/ (rename to skills/data/) - skills/finance/wallet_screening/ (move to skills/compliance/wallet_screening/) - All manifest.yaml files for moved skills - docs/skills/README.md - docs/skills/wallet_screening.md - CONTRIBUTING.md - Any CI or test paths referencing the old paths