fix: make npm recovery validation tag-independent

[regenrek]

Pre-dispatch recovery fix

This is a follow-up to the v0.3.3 npm recovery workflow. It must merge before any recovery dispatch.

Avoided failure

GitHub loads the workflow from main, but the recovery job checks out immutable v0.3.3. The prior workflow invoked scripts/verify-release-archive.sh, which was introduced after that tag and would not exist after checkout. Dispatching would have failed before archive validation. No recovery workflow was dispatched.

Fix and controls

• moves the exact archive-member validator into the recovery workflow step, so it is available after tag checkout
• requires exactly LICENSE, README.md, SHA256SUMS, and model-routing; rejects extras, duplicates, nested paths, and traversal paths before extraction
• runs positive and negative tar fixtures in the workflow step before processing release assets
• removes the unreachable helper scripts to keep one canonical implementation

The recovery’s existing v0.3.3-only confirmation, public-asset SHA256 verification, existing-version refusal, provenance reconstruction, and native/launcher checks remain unchanged.

Review and validation

Independent reviewer: PASS.

• actionlint .github/workflows/release-npm-recovery.yml
• YAML parsing
• cargo fmt --all -- --check
• cargo test -p xtask release
• cached diff check

Do not merge or dispatch without direct execution approval.