Update PDF conversion skills for Nutrient account plans

[vladimir-tikhonov-nutrient]

Summary

• Documents the final conversion model: Standard is free without an account; Vision requires a Nutrient account, API key, or Nutrient CLI license key and uses one Vision page per input page.
• Adds nutrient auth login, status, and logout to both conversion skills, with safe guidance for interactive and unattended use.
• States what stays on the user's computer, what usage data is reported, and how Standard and Vision behave offline.
• Clarifies that query runs locally, requires no account, reports no usage, and uses no Vision pages.
• Fixes SHA-256 verification and hardens installation, locking, rollback, and Windows command dispatch in the bundled wrappers.
• Bumps the PDF to Markdown, PDF to Text, and Query plugin versions.

Reviewer fixes

• Account commands now force a release-channel check and probe the installed binary's actual auth capability. A cached conversion-only binary is rejected with a clear update message when the CDN cannot provide an account-capable release.
• The three wrappers have one byte-identical shared installation region, enforced by validation, so fixes cannot silently drift between copies.
• Wrapper checks are behavioral: fake-CDN tests cover Standard and Vision dispatch, both account launchers, Query, checksum rejection, and the stale 1.4.1 conversion-only regression.
• Customer-text checks only reject retired contract language in the file where it appears; they no longer concatenate prose or require arbitrary exact phrases.

Validation

• python3 scripts/validate-pdf-cli-skills.py — passed locally.
• GitHub Actions validates Linux, macOS, and Windows.
• Shell syntax and ShellCheck pass where available.
• Manifest and marketplace versions are checked together.

Release coordination

Merge after auth-capable signed CLI artifacts are available from the CDN and npm, and after the live plan catalog is complete and valid. The skills contain no hard-coded plan fallback.

• https://linear.app/nutrient/issue/DWSL-496/update-and-publish-nutrient-skills-pr-31-for-the-released-cli-contract
• https://linear.app/nutrient/issue/DWSL-491/finalize-cli-launch-plan-contract-payg-disposition-and-production
• https://linear.app/nutrient/issue/DWSL-494/publish-signednotarized-cli-artifacts-provenance-and-release-channels

[vladimir-tikhonov-nutrient]

review