feat: establish read-only DocForge MCP foundation

tests/fixtures/alpha/docs/content/foundation.md

@@ -0,0 +1,12 @@
++++
+schema_version = 1
+id = "guide.foundation"
+title = "Documentation foundation"
+family = "guide"
+authority = "authoritative"
+status = "approved"
+tags = ["foundation", "canonical"]
+summary = "Defines which Alpha files own documentation facts."
++++
+
+Alpha stores canonical facts in its content directory. Derived indexes may be deleted and rebuilt.

tests/fixtures/alpha/docs/content/proof.toml

@@ -0,0 +1,11 @@
+[[nodes]]
+schema_version = 1
+id = "proof.validation"
+title = "Validation proof"
+family = "proof"
+authority = "derived"
+status = "approved"
+tags = ["proof", "validation"]
+summary = "Records the fixture validation result."
+content = "The fixture contains unique nodes, valid relationships, and confined source paths."
+proves = ["guide.workflow"]

tests/fixtures/alpha/docs/content/workflow.md

@@ -0,0 +1,13 @@
++++
+schema_version = 1
+id = "guide.workflow"
+title = "Editing workflow"
+family = "guide"
+authority = "approved_plan"
+status = "active"
+tags = ["workflow", "editing"]
+summary = "Requires validation before documentation changes are integrated."
+depends_on = ["guide.foundation"]
++++
+
+Editors change canonical nodes, validate relationships, inspect the diff, and rebuild derived output.