Extract Knot Editor to its independent repository

[mark-ik]

Summary

• consume knot-editor and knot-document from immutable public revision c4d15aa66eee46060081902ba8459f01c9c82f98
• patch Knot's Mere-facing Git dependencies back to this checkout so embedded contracts keep one Cargo identity
• cut Djinn over to the external package and remove the two former in-tree source directories
• mark old Knot plans as historical snapshots and point current documentation at the independent product
• keep mere-canvas test debug info to line tables so MSVC can link the Djinn test archive

Receipts

• cargo metadata --locked --format-version 1: one Git identity for each Knot package and one identity for every audited Mere/Genet boundary package
• cargo test -p djinn --lib resident_knot::tests --locked -j1: 1 passed, 58 filtered out
• git diff --check HEAD^: clean

Related

• Knot repository: https://github.com/merely-made/knot-editor
• Turnstone consumer: Consume Knot from knot-editor turnstone#4