chore: sync chore drift (docs, workflows, gitignore, a2ml)

Partial chore-sync for a repo with in-flight source changes. Only
safe-to-split paths committed here (docs, workflow YAML, gitignore,
a2ml migration drift). Source files and dependency manifests left
uncommitted for manual review to avoid creating broken intermediate
states where Cargo.toml and its dependent .rs live in different
commits.

Staged paths:
  - .gitignore
  - src/contracts/README.adoc

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.gitignore

@@ -136,3 +136,11 @@ sync_report*.txt
 *.run.xml
 *-blx.bib
 _minted-*/
+target/
+node_modules/
+_build/
+deps/
+.elixir_ls/
+.cache/
+build/
+dist/

src/contracts/README.adoc

@@ -1 +1,13 @@
 = Contracts Unit
+
+This unit stores executable/consumable contract artifacts that pin
+cross-repo integration boundaries.
+
+Current contract:
+
+- `airborne-submarine-squadron.snapshot-abi.v1.json`
+  - Versioned JS↔WASM `init_state`/`step_state` boundary.
+  - Canonical 29-field snapshot + 5-field input mapping.
+  - Integration boundary note: gameplay/HUD events remain authoritative in
+    game/Gossamer, while Burble can consume mirrored events over
+    Groove/API/FFI for voice/LLM/RTSM workflows.