Sprint 7 Phase 7a: API documentation, schemas, and new RPC methods (Steps 202-206)

- Step 202: docs/AGENT_API.md — comprehensive JSON-RPC API reference with 23 methods
- Step 203: schemas/ — 20 JSON Schema files (8 types, 12 methods) for validation
- Step 204: Expose ContextAPI (getInScopeSymbols, getCallHierarchy, getDependencyGraph) and BatchMutationAPI (applyBatch) via WebSocket RPC
- Step 205: Expose Pipeline operations (runPipeline, parseSource, generateFromAST, projectLanguage) via WebSocket RPC
- Step 206: API schema validation tests — 51/51 assertions pass
- Updated PROGRESS.md with Sprint 5+6 completion, corrected summary table
- Updated FEATURE_REQUESTS.md to reflect implemented items
- Created sprint7_plan.md with 33 steps across 6 phases

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

schemas/methods/applyMutation.schema.json

@@ -0,0 +1,60 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "$id": "https://whetstone-dsl.org/schemas/methods/applyMutation.schema.json",
+  "title": "applyMutation",
+  "description": "Apply a single mutation to the AST",
+  "type": "object",
+  "properties": {
+    "request": {
+      "type": "object",
+      "properties": {
+        "type": {
+          "type": "string",
+          "description": "The type of mutation operation"
+        },
+        "nodeId": {
+          "type": "string",
+          "description": "The unique identifier of the target node"
+        },
+        "property": {
+          "type": "string",
+          "description": "The property name to set"
+        },
+        "value": {
+          "type": "string",
+          "description": "The value to set"
+        },
+        "parentId": {
+          "type": "string",
+          "description": "The parent node ID for insertions"
+        },
+        "role": {
+          "type": "string",
+          "description": "The role/relationship to the parent"
+        },
+        "node": {
+          "type": "object",
+          "description": "The node object to insert"
+        },
+        "properties": {
+          "type": "object",
+          "description": "Additional properties for the mutation"
+        },
+        "preferImports": {
+          "type": "boolean",
+          "description": "Whether to prefer imports over inline definitions"
+        },
+        "strictMode": {
+          "type": "boolean",
+          "description": "Whether to enforce strict validation"
+        }
+      },
+      "required": ["type"],
+      "additionalProperties": false
+    },
+    "response": {
+      "$ref": "../types/MutationResult.schema.json"
+    }
+  },
+  "required": ["request", "response"]
+}