WIP: stage all uncommitted work — sprints 46-221, graduation headers, specialist fleet, test steps 909-1988

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

sprint139_plan.md

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+# Sprint 139 Plan: MCP Backward Compatibility and Deprecation Governance
+
+## Context
+
+Wiring closure must not break existing clients. Sprint 139 adds compatibility and
+deprecation governance for evolving MCP tool surfaces.
+
+---
+
+## Goals
+
+1. Define deterministic backward-compatibility policy for tool changes
+2. Model deprecation lifecycle with explicit timeline states
+3. Add compatibility simulation against client capability profiles
+4. Publish machine-readable deprecation and migration guidance
+
+---
+
+## Steps
+
+### Step 1629: MCP compatibility policy schema (10 tests)
+### Step 1630: Tool deprecation lifecycle model (10 tests)
+### Step 1631: Client capability profile schema (10 tests)
+### Step 1632: Compatibility simulation runner model (10 tests)
+### Step 1633: `whetstone_check_tool_compatibility` MCP tool (8 tests)
+### Step 1634: `whetstone_get_tool_deprecations` MCP tool (8 tests)
+### Step 1635: `whetstone_plan_tool_migrations` MCP tool (8 tests)
+### Step 1636: Compatibility risk packet model (8 tests)
+### Step 1637: Compatibility/deprecation report artifact (8 tests)
+### Step 1638: Sprint 139 integration summary + regression (8 tests)
+
+---
+
+## Architecture Gate
+
+- Compatibility simulation must be deterministic for identical profiles
+- Deprecation states must be explicit and auditable
+- Migration guidance must be structured and machine-readable
+- Max 600 lines per header