Complete DFG-8 adapter proposal support

docs/CONTRACT.md

@@ -1,4 +1,4 @@
-# DocForge 0.5 contract
+# DocForge 0.6 contract
 
 ## Authority boundary
 
@@ -18,7 +18,7 @@ commit when Git is available; it cannot change repository state.
 - Result envelope: `schemas/result.schema.json`, version 1.
 - Changeset schema: `schemas/changeset.schema.json`, version 1.
 - Index schema: version 1, disposable and reproducible.
-- Core, CLI, and MCP server: version 0.5.0.
+- Core, CLI, and MCP server: version 0.6.0.
 
 Schema files describe the generic interchange contract. Runtime validation remains responsible for
 path confinement, source hashing, relationship resolution, dependency cycles, project limits, stale
@@ -94,3 +94,14 @@ process. A project integration may explicitly construct a read-only MCP server f
 `ProjectService` and an optional project-owned context provider. That server exposes only the fixed
 read tool surface. The core does not discover adapters, choose projects or sessions, or import
 project policy.
+
+A proposal-enabled adapter declares confined canonical source, changeset, template, preview, and
+render paths plus fixed writer permissions. It must supply a proposal validator. The core continues
+to enforce optimistic hashes, writer permissions, graph integrity, limits, atomic changeset storage,
+conflict detection, and preview confinement. The adapter validator enforces source-format and
+project semantics that the generic core cannot infer. Generic projects retain the built-in Markdown
+and TOML source-layout validator.
+
+An explicit integration may construct the full fixed MCP surface for a configured adapter project
+and one startup-bound writer. This does not add adapter discovery or canonical application. An
+adapter without proposal settings or validation remains read-only.