docs(wrapper-generator): make the README a self-serve handover guide

[Joywambui-maina]

Changes proposed in this pull request

• Document the derived data files under tools/WrapperGenerator/data/: which script produces each (Derive-CollisionResolutions.ps1, Derive-ParityResolutions.ps1, Update-WrapperParityData.ps1), the -Validate drift gates, and the rule that these files are regenerated, never edited
• Put Invoke-WrapperGates.ps1 in front of the test layers as the front door, with its NOT-RUN / INCOMPLETE semantics
• Replace the stale "no runtime base classes or real auth flow" gap with what src/GraphWrapperRuntime/ actually ships, and the three genuinely open items (per-cmdlet help, SupportsShouldProcess audit, automated Windows PowerShell 5.1 gate leg)
• Refresh the parity ledger numbers to the current corpus (12,355 files: 9,537 matched, 1,431 dispatcher, 396 mismatch, 985 no-oracle, 6 corrected) and point at the command that regenerates the ledger, since numbers in the file are snapshots
• Break the 362 unresolved name mismatches into six measured families (function-with-params 142, cast-shape 80, case-only 72, embedded-Get 27, verb remap 23, Io-defect 18) with a resolution path for each
• Add the missing source-file rows (DerivedCollisionResolutions.cs, GeneratorConstants.cs, StderrLogger.cs, data/) to the source-file table