docs: align dependency resolution with current contract model

[SamCT86]

Summary

• remove retired ### Services, ### Ensures, and system/service dependency terminology from deps.md
• describe dependency discovery around use and pattern: references only
• align Forme/VM dependency wording with current Requires → Maintains and Parameters → Returns contracts
• add a focused regression assertion so retired dependency syntax is not reintroduced

Use Case / Run Evidence

Issue #165 documents that deps.md still teaches dependency behavior that the current language docs have retired. The stale wording can cause agents and human authors to reach for ### Services, ### Ensures, or the removed system kind.

Closes #165.

Design Boundary

This is a documentation/conformance fix only. It does not change VM, Forme, CLI, dependency resolver, or runtime behavior. The changes stay in skills/open-prose/deps.md plus the existing skill-meta conformance suite.

Examples

The install scan now enumerates use and pattern: references, and the VM section describes imported functions through ### Parameters / ### Returns rather than retired service/system contracts.

Testing

• corepack pnpm test:skill -- tests/open-prose/skill-meta/skill-meta.test.ts → 28/28 pass
• full corepack pnpm test:skill comparison on exact upstream main (770cebc9e03a7150a73bd454b7a6da307595ff9d): baseline 290 pass / 11 fail; patch 291 pass / the same 11 fail
• git diff --check → pass

The 11 full-suite failures are pre-existing on current upstream main; this patch introduces no additional failure and adds one passing regression test.

Residual Risk / Follow-ups

This PR intentionally does not repair unrelated current-main conformance failures or change language semantics. It only removes stale dependency documentation and guards that boundary.