Add Sprints 46-59: governance, porting foundation, and language graduation prep (Steps 689-828)

Sprints 46-58 implement the cross-language porting foundation: language-to-IR
adapters, equivalence checking, gate validation, legacy ingestion, managed/dynamic
families, low-level/logic-actor semantics, debug workflow tooling, AST-native
family tools, Rust/CPP raising tools, system-level orchestration, query family,
and porting gates. Sprint 59 adds the governance layer (policy packs, review
boards, waiver packets, ambiguity triage, decision ledger) with the
whetstone_review_porting_decision MCP tool.

Also includes: sprint plans 46-130, MCP taskitem pipeline scripts,
CLAUDE.md, docs, and full test matrix (steps 689-828).

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

docs/SPRINT46_FOUNDATION.md

@@ -0,0 +1,19 @@
+# Sprint 46 Foundation
+
+This document captures the baseline artifacts introduced for Sprint 46.
+
+## Components
+
+- Semantic IR schema: `editor/src/SemanticCoreIR.h`
+- Support tiers and gate mapping: `editor/src/LanguageSupportTier.h`
+- Capability matrix model: `editor/src/LanguageCapabilityMatrix.h`
+- Migration contract checks: `editor/src/MigrationAcceptanceContract.h`
+
+## Example Artifacts
+
+- Semantic IR example: `docs/examples/sprint46_semantic_core_example.json`
+
+## Notes
+
+- All schema models are deterministic JSON serializable.
+- Unknown tags/fields are preserved where possible for forward compatibility.