decouple abstraction phase2: dub sub-package splitsisudoc-spine_v0.21.0

Declare sisudoc.abstraction as a dub sub-package (spine:abstraction)
within the existing dub.json. The sub-package's sourcePaths cover
exactly the abstraction-side clusters that were freed from io_out
edges in phase 0 and phase 1:

  - src/sisudoc/abstraction (package surface + ssp serialiser)
  - src/sisudoc/meta        (per-document abstraction)
  - src/sisudoc/io_in       (file/pod ingress)

Its declared dependencies are spine:dyaml and spine:imageformats
only - no d2sqlite3, no io_out. The main "spine" package adds
spine:abstraction to its dependencies and lists those three
directories in excludedSourceFiles so dub does not compile the
abstraction-side sources twice when the executable is built with
--combined (as the nix derivation does).

(assisted by Claude-Code)

0 files changed, 0 insertions, 0 deletions