v0.92.0

• 0.92 technical-debt sweep: correctness, $seed hardening, de-duplication (#727)
• dotnet: add $seed namespace writers (parity with Python/WASM)
• refactor(core): unify $ext/$seed into one out-of-band Meta concept
• Cleanup: simplify QuillWorld::font to a single expression
• Cleanup: de-narrate comments, sync canon binding tables with .NET
• dotnet: fix stale schema version (CI) + review-flagged polish
• docs(migration): cover the !fill → !must_fill rename in the 0.92 guide
• dotnet: fix native-lib copy to test project + two correctness bugs
• Remove Document.seed(kind) for strict ext/seed symmetry
• dotnet: expose $seed on the Card DTO
• refactor(dotnet): rename engine class Quillmark -> QuillmarkEngine
• Reject !fill: treat as a noncanonical tag, not a fill alias
• Fix binding build break + warn on unsupported fill positions
• fix(dotnet): resolve engine type in test namespace (CS0426)
• docs(dotnet): trim README to a dense, consumer-focused surface
• Address review nits: loud divergence, docs, coverage
• Add storage schema 0.92.0: persist nested !must_fill
• docs(canon): consolidate binding overviews into BINDINGS.md
• feat($seed): reject $seed on composable cards (root-only, like $quill)
• docs: move dotnet binding into canon, delete DESIGN.md
• docs: reframe QmBytes by-value return as a tested assumption, not a defect
• Carry nested !must_fill across the live wire (CardWire)
• Address review: trap FFI panics, fix depth-limit asymmetry, Equals contract
• Detect nested !must_fill on sequence-item inline first key
• docs($seed): correct two claims flagged in review
• Fix invalid '--' inside XML comment in Quillmark.csproj
• fix(docs): drop canon links that break mkdocs --strict
• Promote .NET binding: CI test job, NuGet release, first-class docs
• Spike: .NET binding symmetrical to the Python binding
• Capture and round-trip nested !must_fill markers
• Make QuillValue an annotated value tree (fill on nodes)
• fix(bindings): bump currentSchemaVersion to 0.92.0; add $seed JS test
• Rename !fill tag to !must_fill (accept !fill as deprecated alias)
• docs($seed): document the per-kind seed-overlay key across canon and spec
• test($seed): cover parse/emit/storage, overlay layering, advisory validation
• feat(core): first-class $seed key for per-card-kind seed overlays
• Remove RenderSession and canvas-preview APIs from Python binding (#722)