docs: coverage-statement-block (S2 Phase 1)

32 assertions over 6 functions; per Fault-Injection-Audit-Convention
2026-05-16. Documents Tested-Surface + Structurally Untestable +
Deferred items.

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

README.md

@@ -1,3 +1,31 @@
 # lib-core.api-discovery-test
 
-Test-lib for `lib-core.api-discovery` (Tests-as-Libs per ADR-0037). Coverage-Statements added incrementally.
+Test-lib for `lib-core.api-discovery` (Tests-as-Libs per ADR-0037).
+
+## Coverage Statement
+
+Per Fault-Injection-Audit-Convention (2026-05-16):
+
+| Function | Assertion-Count | Coverage |
+|---|---|---|
+| `parse_lua_surface` | 7 | Happy-path (2 public + 1 private), empty-source edge |
+| `parse_readme_api` | 4 | Standard H3-pattern, no-API-section edge |
+| `diff_surface` | 5 | Equal (no diff), surface-superset (missing), doc-superset (stale) |
+| `grep_engine_calls` | 5 | 3 unique calls, no-calls edge |
+| `generate_topology_block` | 6 | Lib-with-deps+engine, asset-lib (no deps, no engine) |
+| `validate_readme_structure` | 5 | Complete core, missing-API core, community-tier-no-enforcement |
+| **TOTAL** | **32** | |
+
+### Tested-Surface
+- All 6 public functions of `lib-core.api-discovery` v0.1.0.
+
+### Structurally Untestable
+- Idiomatic-edge: `M.foo = function ... end` mit Multi-Line-Body wird durch pattern-line-match abgedeckt; very-creative-patterns (z.B. dynamic `_ENV[k] = function...`) sind by-design out-of-scope.
+- Doc-quality (sind die Function-Descriptions akkurat?) — sentiment-level question, kein assertion-target.
+
+### Deferred
+- Mutation-Audit der Test-Lib selbst (analog 2026-05-16 Test-Coverage-Audit) — Folge-Slice.
+
+## Running
+
+Wird automatisch via `--test-libs=lib-core.api-discovery-test` ausgeführt (Smoke P0-S-batch Stage).