docs: seed CHANGELOG.md (Keep-a-Changelog format) (#45)

## Summary
Adds an initial `CHANGELOG.md` in Keep-a-Changelog format. Recent
commits are bucketed into Added/Fixed/Changed/Documentation/CI from
their conventional-commit prefixes.

Closes **Row-2 Phase 3** of the 2026-05-26 estate tech-debt audit chain
for this repo. The audit
([standards#197](hyperpolymath/standards#197))
flagged 180/279 repos missing CHANGELOG (65% gap).

## Adopting auto-regeneration
For ongoing auto-regeneration, adopt the
[`changelog-reusable.yml`](https://github.com/hyperpolymath/standards/blob/main/.github/workflows/changelog-reusable.yml)
workflow
([standards#206](hyperpolymath/standards#206))
in this repo's CI. Uses the canonical
[`templates/cliff.toml`](https://github.com/hyperpolymath/standards/blob/main/templates/cliff.toml).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: hyperpolymath

CHANGELOG.md

@@ -0,0 +1,76 @@
+<!--
+SPDX-License-Identifier: MPL-2.0
+SPDX-FileCopyrightText: 2026 Jonathan D.A. Jewell (hyperpolymath)
+-->
+
+# Changelog
+
+All notable changes to `januskey` will be documented in this file.
+
+This file is generated from conventional commits by the
+[`changelog-reusable.yml`](https://github.com/hyperpolymath/standards/blob/main/.github/workflows/changelog-reusable.yml)
+workflow (`hyperpolymath/standards#206`). Adopt the workflow in this repo's CI to keep this file in sync automatically — see
+[`templates/cliff.toml`](https://github.com/hyperpolymath/standards/blob/main/templates/cliff.toml)
+for the canonical config.
+
+The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/);
+this project aims to follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+
+- feat(crg): add crg-grade and crg-badge justfile recipes
+- feat(crg): add Current Grade badge anchor to READINESS.md
+- feat: add idrisiser Idris2 proof wrappers for JanusKey cryptographic core
+- feat: blitz — wire all tests, add property-based + regression, fix benchmarks, READINESS.md
+- feat: add E2E, P2P, aspect tests + criterion benchmarks
+- feat: add Zig FFI implementation + C header + integration tests
+- feat: complete Idris2 ABI — Foreign.idr + Proofs.idr
+- feat: add Idris2 ABI proofs — TypeLL Levels 1-12
+- feat: add stapeln.toml container definition
+- feat: deploy UX Manifesto infrastructure
+
+### Fixed
+
+- fix(ci): bump a2ml/k9-validate-action pins to canonical (#33)
+- fix(ci): sync hypatia-scan.yml to canonical (#32)
+- fix(ci): adopt canonical hypatia-scan.yml (#31)
+- fix(ci): Phase-2 fleet submission must not fail the security gate (#30)
+- fix(ci): hypatia-scan workdir (${{ env.HOME }} resolves empty) (#29)
+- fix(januskey): sweep .expect("TODO: handle error") — 166 sites cleared
+- fix: replace 60 unwrap() calls with expect() in security-critical modules
+- fix: quote $$ and use printf in setup.sh
+- fix: correct 'Provably Reversible' claim — proofs are pending, not done
+- fix(scorecard): enforce granular permissions and add fuzzing placeholder
+
+### Changed
+
+- refactor: migrate 6SCM → 6A2 (.scm → .a2ml format)
+
+### Documentation
+
+- docs(security): draft MCP-exposure threat model (AI-authored, pending human sign-off)
+- docs: add M2 estate audit report (2026-04-04)
+- docs: substantive CRG C annotation (EXPLAINME.adoc)
+- docs: add EXPLAINME.adoc — prove-it file backing README claims
+- docs: add ARCHITECTURE.md — reversibility stack junction point
+- docs: update SCM files with project information
+- docs: add CONTRIBUTING.md
+- docs: add checkpoint files for state tracking
+
+### CI
+
+- ci(rust): convert rust-ci.yml to thin wrapper (standards#174) (#39)
+- ci: redistribute concurrency-cancel guard to read-only check workflows (#35)
+- ci: bump actions/upload-artifact SHA to current v4 (#27)
+- ci: SHA-pin hyperpolymath validate-actions in dogfood-gate
+- ci: restore Dependabot security path + wire auto-merge
+
+## Pre-history
+
+Prior commits to this file's introduction are recorded in git history but not formally classified into Keep-a-Changelog sections. To backfill, run `git cliff -o CHANGELOG.md` locally using the canonical [`cliff.toml`](https://github.com/hyperpolymath/standards/blob/main/templates/cliff.toml) — this is one-shot mechanical work.
+
+---
+
+<!-- This file was seeded by the 2026-05-26 estate tech-debt audit follow-up (Row-2 Phase 3); see [`hyperpolymath/standards/docs/audits/2026-05-26-estate-documentation-debt.md`](https://github.com/hyperpolymath/standards/blob/main/docs/audits/2026-05-26-estate-documentation-debt.md). -->