feat: add PURL copy semantics

[indexzero]

Summary

• keep vlurp owner/repository as the easy, first-documented fetch interface
• add precise vlurp SOURCE... DEST copying using pkg:github PURLs
• preserve repository shorthand, --filter, and all named presets as first-class supported interfaces
• add repeatable, case-sensitive --glob and case-insensitive --iglob transfer patterns; leading ! excludes matches
• let --preset compose with PURL copy operands, with explicit transfer patterns refining preset rules
• copy source matches with familiar basename semantics and secure destination preflight
• integrate PURL sources and transfer rules with lineage, verification, catalogs, batch manifests, pin, outdated, and upgrade
• add a minor changeset and document the cohesive operand/pattern model

vlurp \
  'pkg:github/mattpocock/skills#skills/in-progress/writing-*' \
  ./skills/ \
  --preset skills \
  --iglob '**/skill.md'

The operands determine source selection and destination placement. Presets and transfer globs determine which files beneath each selected source are copied.

Verification

• pnpm test — 142 passed
• pnpm lint — passed with 2 pre-existing scanner warnings
• pnpm test:e2e:ci — live GitHub redirect, packed-install, and combined preset/glob/iglob PURL coverage passed; Linux executes the PTY cases in CI
• git diff --check

The branch is rebased onto the post-2.0.1 main release commit.