Sprint 3 plan and docs: adopt canonical annotation system from annotations/Memory strategy.md

- Add Sprint 3 plan (37 steps, global 39-75) with canonical memory annotations,
  test quality requirements, global step numbering, and Sprint 2 overlap notes
- Refactor all docs to use canonical annotation families (@Deallocate, @Lifetime,
  @Reclaim, @Owner, @Allocate) replacing simplified @deref 4-strategy system
- Replace @perf with canonical @Hot/@Cold, @Inline, @Pure from annotations/6 optimization
- Replace @memory-footprint, @execution-mode, @deref-explicit with canonical equivalents
- Update REQUIREMENTS_OVERVIEW, SPRINT_1_REQUIREMENTS, SPRINT_2_PLAN, SPRINT_2_VISION,
  C++ Implementation Roadmap, example files, and progress report
- Remove duplicate bonus steps 41-42, consolidate Phase 3h from 7 to 4 steps

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

docs/SPRINT_2_VISION.md

@@ -201,7 +201,7 @@ Benefits:
 │                                                                 │
 │  Annotations:                                                   │
 │  ┌─────────────────────────────────────────────────────────┐   │
-│  │ [@deref: batched ▼]  [@complexity: ___]  [+ Add]        │   │
+│  │ [@Reclaim(Tracing) ▼]  [@complexity: ___]  [+ Add]       │   │
 │  └─────────────────────────────────────────────────────────┘   │
 │                                                                 │
 │  [Continue to Body →]                                          │
@@ -271,7 +271,7 @@ Benefits:
 │  Function: process_data                                         │
 │  ├── params: [(items, List[int]), (threshold, int, default=10)]│
 │  ├── returns: List[int]                                        │
-│  ├── @deref: batched                                           │
+│  ├── @Reclaim(Tracing)                                         │
 │  └── body:                                                      │
 │       └── Return                                                │
 │            └── Call: list                                       │
@@ -651,7 +651,7 @@ Sprint 1 (MPS) provides:
 - Core AST node definitions
 - SemAnno annotation schema
 - Python ↔ C++ projection patterns
-- Memory deref strategy examples
+- Memory strategy annotation examples (canonical system: `@Deallocate`, `@Lifetime`, `@Reclaim`, `@Owner`, `@Allocate`)
 
 Sprint 2 consumes Sprint 1 by:
 - Porting AST definitions from MPS to C++ classes (initially)