Add matching geometry review and cleanup fixes in 0.4.0

[the3dcoder]

A model exported to STL, OBJ, and PLY can share the same triangles while having different file bytes and names. Model Scout 0.4.0 adds a separate matching-geometry review with paired previews, explicit candidate selection, and keeper checks across pages before the existing verified copy/move workflow.

Comparison is local and bounded, with cancellation, fingerprint-bound caching, and explicit retry. It ignores placement and triangle/vertex order while preserving scale and orientation. Units, appearance, rotation normalization, and different tessellations are outside this initial scope; candidates require review.

Also fixes lost exact-duplicate keeper choices when paging, review opening during partial hashing, saved cost estimates disappearing after in-app moves, and stale moved-file inspectors. Git attributes fix the Windows line-ending failure found in the baseline hosted run. Existing Three.js loaders are reused; research and limitations are documented.

Validation:

• 22 core/feature tests, formatting, build, and production-dependency audit pass locally.
• Six source desktop workflows and five packaged desktop workflows pass, including actual CAD/WASM loading, cross-format comparison, paired previews, minimum window layout, 21-group geometry review, and 51-group exact-duplicate pagination.
• Windows portable 0.4.0 build completes; the binary is unsigned.
• Read-only discovery on the owner's large library reports 21,734 matches, zero errors, and a 1.63-second scan. This is discovery timing, not full geometry-analysis timing; private receipts are excluded from the repository.

The 0.3.0 baseline was pushed to main before these changes began. This branch contains the 0.4.0 update; no user model files were moved or changed.

Hosted verification: both the branch Windows run and PR Windows run pass. The complete 0.4.0 ZIP was assembled locally and checked for matching executable bytes, runtime notices, all four importer source archives, and its SHA-256 checksum. The release binary has not been published to GitHub Releases.