test(launcher-test): cheap-fill M3 gap + Coverage Statements (Test-Cov Phase 2.7)

3 mutations tested. 2 caught, 1 uncaught (M3: unknown-state fallback returns nil).
Cheap-fill: added fsm.next("garbage_state", "esc") == "garbage_state" assertion.

README.md

@@ -0,0 +1,49 @@
+# sporel-module-lib-sporel.launcher-test
+
+P.3.4 reference test-module — validates `lib-sporel.launcher` FSM contracts
+and engine-surface existence via the `engine.test.*` assertion surface.
+
+- Module-ID: `lib-sporel.launcher-test`
+- Version: `0.1.0`
+- Kind: `test-module` (headless; runs init() once + exits)
+- Note: Embeds its own byte-identical copy of `fsm.lua` (Sporel-resolver does
+  not resolve module-as-dep; drift guarded by smoke.sh P0-S15-pre hash check).
+
+## Run
+
+```bash
+Sporel.exe --test-libs=lib-sporel.launcher-test
+```
+
+Output is TAP version 13 on stdout; exit-code = failure-count (0 = all pass).
+
+## Coverage Statements (2026-05-16 Fault-Injection Audit)
+
+Verified via deliberate-mutation in the launcher-test fixture's own `fsm.lua`
+copy; mutations reverted after observation.
+
+### Caught Mutations
+
+| # | Mutation | Caught by |
+|---|---|---|
+| M1 | `STATE_LIST + "esc"` returns `STATE_LIST` instead of `STATE_QUIT_CONFIRM` | Assertion "list+esc -> quit_confirm" (ok 1) |
+| M2 | `STATE_QUIT_CONFIRM + "enter"` returns `STATE_QUIT_CONFIRM` instead of `EXIT` | Assertion "quit_confirm+enter -> exit" (ok 3) |
+
+### Uncaught Mutations (Gaps)
+
+| # | Mutation | Why uncaught | Severity |
+|---|---|---|---|
+| M3 | Fallback `return state` removed (unknown state returns nil) | No test calls `fsm.next` with an unrecognized state string | Low |
+
+**Resolution per Gap:**
+- Gap M3: Cheap-fill applied — added assertion `fsm.next("garbage_state", "esc") == "garbage_state"` to verify unknown-state passthrough (commit see below).
+
+### Cheap-Gap-Fills Applied
+
+| Gap | New Assertion | Re-Inject Verifies |
+|---|---|---|
+| M3 | `unknown state passes through unchanged` — `fsm.next("garbage_state", "esc")` must equal `"garbage_state"` | ✓ |
+
+### Tested Production-Lib Surface
+
+`lib-sporel.launcher` v0.1.0 (FSM component) — Tests cover: all 5 explicit FSM transitions (`list+esc`, `quit_confirm+esc`, `quit_confirm+enter`, `quit_confirm+click_yes`, `quit_confirm+click_no`), stability for unhandled events (`list+click_module`), unknown-state passthrough, and engine-surface existence for `engine.module.list`, `engine.module.dir_of`, `engine.render.draw_text`, `engine.render.measure_text`.