docs(skills): use current contracts and conditional guidance

[drewstone]

Agents loading Runtime skills currently receive repeated API catalogs and instructions for unrelated tasks.
The code-mode guide also shows a call without the required runner.

Use maintained source links for exact contracts and conditional guides for profile authoring, graph details, improvement, and Runtime code execution.
Keep recursion grants, immutable evidence, shared accounting, completion checks, and atomic activation requirements visible.
Preserve historical graph case and generation records while removing their obsolete execution recipe.
Keep exact target identities in generated benchmark cases so comparisons remain reproducible.

Validation:

• 82 tests pass across skill validation, tool names, code-mode execution, and graph behavior.
• All six skill entrypoints pass frontmatter validation.
• Thirteen source links resolve against the current remote tree.
• Package dry run includes all six entrypoints and all five conditional references.
• Independent source review found no blocking regression.

These checks verify contracts and packaging.
They do not measure whether the revised writing improves agent task performance.