[AGiorgetti]

Mammoth.LiteMapper.Generator 4.0.1 placed its PDB under lib/netstandard2.0 while its DLL exists only under analyzers/dotnet/cs, causing NuGet symbol validation to reject an otherwise matching DLL/PDB pair. Explicitly pack the generator DLL and portable PDB at the analyzer path and remove the build-output-removal workaround.

Add a shared, nonshipping validator for package metadata, archive-relative paths, portable format, PE/PDB identity and compiler checksum. Use it in shipping-package regressions, release CI before artifact upload, and manual publishing even with -SkipValidation or dry runs. Negative fixtures cover path, identity, checksum, portability and metadata failures; native-command tests prove validation failures stop publication. Existing CI coverage and release gates remain in place.

Targets develop, which contains the published 4.0.1 release; release/4.0.1 has been removed. The corrected original 4.0.1 .snupkg was prepared and delivered separately for a human upload. This PR does not publish packages or replace the immutable 4.0.1 .nupkg.

Validation

• Shipping regression failed on the original generator PDB path; ten fixture checks passed. Three publication-gate regressions failed before integration.
• Final committed symbol/gate checks: 16 passed; release/native safeguards: 60 passed. Negative path, identity and checksum fixtures pass, alongside no-PDB and partial-symbol controls.
• Release solution build passed, with two existing generator-test dependency audit warnings.
• Local correctness: 1,083 generator tests, five runtime tests and one integration test passed. Full local package suite: 289 passed, one trimmed-publish timeout at the unchanged ten-minute bound, and one Native AOT skip because the platform linker is absent.
• Local benchmark launches and allocation measurements were excluded to avoid the separate allocation investigation. Existing CI still runs its full coverage.
• Independent static review found no remaining actionable issues.
• Exact-head CI at 579f8cc80bb61d33e517cfcad03646af099cd60b completed successfully: both full Windows/Linux jobs and all six Roslyn 4.8/4.14/5.9 jobs passed. The full jobs retain required trimming/Native AOT and existing benchmark coverage. Release packaging, artifact handoff and publication jobs were skipped for this PR, as intended. CI run.