Add a replayable full-system simulator on a fake clock (#284)

A scenario is a JSON file under cmd/mavend/testdata/scenarios: a start
instant, a script of canned model answers, and a list of steps at "HH:MM".
Each step does one thing — say, audio, signal, arrive, tick, fault — and
then asserts on what she said, what was sent, which ecosystem services were
called, and what landed in the intake journal.

Between those boundaries the real components run: the real router cascade
(stage0, the LLM router over a scripted completer, the classifier
underneath it), the real store, the real reactive handler, the real tick
loop, and the same intake-decorated ipc.CoreAPI the daemon wires. What is
faked is only what a test cannot have: the model, the microphone, the
speaker, the delivery sink, and the ecosystem HTTP services.

Time is a single fakeClock threaded into every reader — the handler, the
intake publish stamp and tick(ctx, now) — so there is no time.Now() on the
replay path and a scenario is reproducible. TestSimulatorIsDeterministic
enforces that by replaying twice and diffing the transcripts byte for byte;
advanceTo refuses a step that goes backwards.

Two scenarios ship. morning_missed replays #284's own description: he
appears at the desk, a feed item, a mail candidate and a relayed
notification arrive through the morning, two ticks pass, and the assertions
are as much about nothing being sent at him unprompted as about what she
said. evening_degraded picks up the tier-2 pipeline case #288 deferred
here — a golden WAV through the STT seam to a written fact — and then puts
the ecosystem into 503 and checks that the proactive loop stays quiet and
that intake keeps working without it.

This is test-only code. Nothing in the production binaries changed, so the
daemon behaves identically when no scenario is running.

`make simulate` runs them verbose so the transcript is readable; `make
test` runs them with everything else.

Vikunja #284

Makefile

@@ -16,7 +16,7 @@ PIPER_BIN     := $(shell pwd)/deps/piper/piper
 PIPER_MODEL   := $(shell pwd)/models/tts/ru_RU-irina-medium.onnx
 PIPER_ESPEAK  := $(shell pwd)/deps/piper/espeak-ng-data
 
-.PHONY: stt-fixtures test-stt-golden all build build-stt build-tts build-daemon build-client build-waked build-web build-poll build-caldav clean test fmt-check vet run-stt run-tts run-web download-embedder deps-go eval-router eval-recall eval-phrasing eval-models
+.PHONY: simulate stt-fixtures test-stt-golden all build build-stt build-tts build-daemon build-client build-waked build-web build-poll build-caldav clean test fmt-check vet run-stt run-tts run-web download-embedder deps-go eval-router eval-recall eval-phrasing eval-models
 
 all: build
 
@@ -91,6 +91,14 @@ vet:
 	CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" LD_LIBRARY_PATH="$(shell pwd)/deps/lib" \
 		$(GO) vet ./internal/... ./cmd/...
 
+# simulate — replay every scripted day under cmd/mavend/testdata/scenarios
+# through the real router, store, tick loop and intake journal, on a fake clock
+# (Vikunja #284). Verbose so the transcript of each scenario lands in the
+# terminal. Also runs as part of `make test`; this target is for reading it.
+simulate:
+	CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" LD_LIBRARY_PATH="$(shell pwd)/deps/lib" \
+		$(GO) test -v -count=1 -run TestSimulator ./cmd/mavend/
+
 test: fmt-check vet
 	CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" LD_LIBRARY_PATH="$(shell pwd)/deps/lib" \
 		$(GO) test -race -coverprofile=coverage.out ./internal/... ./cmd/...