feat: define deterministic renderer font records

[Happypig375]

Summary

• define the versioned little-endian CMR1 renderer-record envelope and deterministic section directory
• add strict standalone bounded reader/writer validation for schema, endian, offsets, counts, overlap, truncation, reserved bytes, duplicate tags, hashes, and trailing data
• preserve Prototype deterministic bundled-font artifact formats #319 source identities and emit compact identity-only records for all three bundled faces; full cmap/outline/MATH sections remain scoped to later children
• generate binary and C# representations from the same logical model and verify checked-in artifacts by immutable temporary regeneration
• document format compatibility, limits, ordering, AOT/trimming behavior, and artifact roles without changing runtime rendering

Testing

• FontBlobTests + RendererRecordTests: 9 passed
• Release test-project build: 0 warnings/errors; actual generated C# compiled
• legacy CSMF1, compact CMR1, and generated-C# regeneration/verification passed for all three faces
• corrupt CMR1 reserved-byte copy was rejected; supplied artifact hashes remained unchanged during verify
• scoped formatting and git diff --check passed
• independent architecture review approved the compact final design

Stack

This PR is based on issue-191-precomputed-fonts / #325 and implements the first actionable schema child of #320.

Closes #327