p0-1: wire-schema stubs, doc/spec stubs, V001 migration, fixtures

- docs/wire-schema/v1/ ships 7 schema stubs (citation, search_hit,
  answer, ingest_report, doc_summary, chunk_inspection, doctor) that
  pin schema_version + required fields per design §2. Full property
  validation lands in later phases.
- docs/spec/ ships 7 markdown stubs each linking to the canonical
  frozen design (domain-model, ids, canonical-document, chunk-policy,
  citation-policy, module-boundaries, ai-generation-guidelines).
- migrations/V001__init.sql contains only schema_meta + migrations
  tables per design §5.1; data tables ship in P1-6/P2-1/P3-3.
- fixtures/ has the 11 subdirectories every downstream task references
  (markdown, source-fs, search/{lexical,hybrid}, embed, vector, rag,
  eval, image, pdf, audio). Empty subdirs use .gitkeep so they track.
  fixtures/markdown/ ships the 3 phase-0 fixtures: simple-note.md,
  nested-headings.md, code-and-table.md.

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

docs/wire-schema/v1/chunk_inspection.schema.json

@@ -0,0 +1,32 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://kb.local/wire/v1/chunk_inspection.schema.json",
+  "title": "ChunkInspection v1",
+  "description": "Stub schema — declares the schema_version label and the required fields per design §2.6.",
+  "type": "object",
+  "required": [
+    "schema_version",
+    "chunk_id",
+    "doc_id",
+    "doc_path",
+    "heading_path",
+    "text",
+    "source_spans",
+    "block_ids",
+    "token_estimate",
+    "chunker_version"
+  ],
+  "properties": {
+    "schema_version":  { "const": "chunk_inspection.v1" },
+    "chunk_id":        { "type": "string" },
+    "doc_id":          { "type": "string" },
+    "doc_path":        { "type": "string" },
+    "heading_path":    { "type": "array", "items": { "type": "string" } },
+    "text":            { "type": "string" },
+    "source_spans":    { "type": "array" },
+    "block_ids":       { "type": "array", "items": { "type": "string" } },
+    "token_estimate":  { "type": "integer", "minimum": 0 },
+    "chunker_version": { "type": "string" },
+    "embeddings":      { "type": "array" }
+  }
+}