docs: changelog, docs/ set, CONTRIBUTING, LICENSE

Bring floret-kit up to the family's repo conventions:
- CHANGELOG.md (Keep a Changelog) — what each module added.
- README.md — full module table (core-time/core-crash/identity/components) +
  consumption notes and a docs index.
- docs/README.md (index), docs/ARCHITECTURE.md (module layering, the submodule +
  composite-build consumption model, JVM vs android-library, the reproducibility
  rules, the share-mechanics-not-look contract), docs/ROADMAP.md (extracted vs
  deferred vs deliberately-not-shared, from the cross-app survey).
- CONTRIBUTING.md — the no-app-coupling rules, how to add a module, how an app
  adopts the kit.
- LICENSE (MIT, matching the apps).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/README.md

@@ -0,0 +1,26 @@
+# floret-kit — documentation
+
+floret-kit is the shared **Material 3 Expressive design system + plumbing** for
+the Floret family of Android apps
+([Calendula](https://gitea.jeanlucmakiola.de/makiolaj/calendula),
+[Agendula](https://gitea.jeanlucmakiola.de/makiolaj/agendula), and future
+siblings). It is consumed from source as a git submodule + Gradle composite
+build. See the top-level [`../README.md`](../README.md) for the pitch.
+
+## Index
+
+| Doc | What it covers |
+|---|---|
+| [`ARCHITECTURE.md`](ARCHITECTURE.md) | How the kit is built and **consumed** — the module layering, JVM vs Android-library modules, the submodule + composite-build model, and the reproducibility rules. Start here. |
+| [`ROADMAP.md`](ROADMAP.md) | **What's extracted, what's deferred, and what's deliberately not shared** — the module status and the divergence decisions from the cross-app survey. |
+| [`../CONTRIBUTING.md`](../CONTRIBUTING.md) | The practical how — adding a module, the no-app-coupling rules, build/test, and how an app adopts the kit. |
+| [`../CHANGELOG.md`](../CHANGELOG.md) | Keep a Changelog; what each module added. |
+
+## The one principle
+
+> Share the **mechanics**, keep the **look** per-app.
+
+Theme machinery, plumbing, and component primitives are shared; seed colours,
+palettes, identity chips, and app-specific wording stay in each app. This is what
+lets the family read as one design language without homogenising apps that are
+meant to have distinct personalities.