initial: composition-test v0.1.0 — 14 assertions

Phase-A.1 test-lib for lib-core.composition. Covers define_template,
create, list_by_template, list_by_tag, destroy, list_templates.

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

README.md

@@ -0,0 +1,33 @@
+# lib-core.composition-test
+
+Test-lib for `lib-core.composition` v0.1.0. Follows the P.2.4
+Test-Module-Pattern: exports `run_tests(ctx)` invoked by the engine's
+`--test-libs` runner; uses `engine.test.*` for TAP-style output.
+
+**Version:** 0.1.0
+**Lib-ID:** lib-core.composition-test
+**Role:** test
+**Requires:** lib-core.composition v0.1.0
+**Tags:** test, composition
+
+## Coverage (14 assertions)
+
+| Group | Count | What |
+|---|---|---|
+| `define_template` | 4 | happy-path register, missing-id error, duplicate error, slot-block error (Phase-D trigger) |
+| `create` | 4 | returns non-nil handle, override applies, nested-flatten works, template-default survives |
+| `list_by_*` | 3 | template-list count, tag-list count, unknown-template empty |
+| `destroy` | 2 | template-index grows on second create, shrinks on destroy |
+| `list_templates` | 1 | non-empty after define |
+
+## Run
+
+Headless via the engine's test-libs orchestrator:
+
+```bash
+~/Projects/Sporel/sporel-engine/build/sporel \
+    --test-libs=lib-core.composition-test
+```
+
+(or however the local dev convention runs `engine.test.*` lib-tests —
+see `engine/scripts/run-tests.sh` for the canonical invocation).