[devin-ai-integration]

What and why

ExecuteStateRequest.advance and ExecuteActionRequest.advance are in the proto and honoured by sysml-grpc, but the in-browser engine's JSON mirrors (JExecuteStateRequest, JExecuteActionRequest) lacked the field, so sysml-engine always ran a machine to quiescence and an action to completion. The Node client already sends advance; only the engine ignored it. The homepage hero needed a run that stops mid-way to show a clocked state machine, which is what advance is for.

Engine

• The advance-aware runs move out of the gRPC package into the runtime, beside StateOutcomePerformedBy: (*Context).StateOutcomeAdvancedBy, ActionOutcomeAdvancedBy and ExecuteActionAdvancedBy (with runtime.ErrNotCompleted, formerly the grpc package's). run_options.go delegates to them, so the service and the engine share one implementation and the two request mirrors cannot drift on this field.
• JExecuteStateRequest.advance and JExecuteActionRequest.advance are read by the engine with the service's validation (finite, non-negative, otherwise InvalidArgument).
• seed, draws and clock_step stay out of the engine's mirrors: they did not fall out of this change (the engine serves no exploring schedule and has no draw policy plumbing), so they are left for their own change.
• Nothing in the response was added: the service does not report the next clock due time, so the page does not show one either rather than computing it.

Hero (editors/vscode/src/landing, overrides/home.html)

• A third tab, "Mission phases on the clock" (scene phases), renders #state:MissionSequence::MissionPhases from examples/runtime-showcase/mission-sequence.sysml. Run calls ExecuteState on the engine with performerSymbolId: MissionSequence::mission, advance: 400000, trace: true, then replays the trace the engine recorded: each state lit as its entry record comes, the token travelling each fired transition, the status line reading the clock from the records (t = 9,000 s · transition: prelaunch -> translunarCoast (event: time)), ending with the engine's answer: the states visited, finalTime, and whether the last state visited is the machine's final state.
• The variant toggle "Advance to 800,000 s" runs the same program with advance: 800000: the path continues through transEarthCoast and recovered to done, which the trace puts at t = 702,000 s.
• LandingModel gains a machine shape for a state view (LandingMachine: the states by name, lifted out of the state def box; LandingState keeps kind and initial) beside the part-shaped composition, so a state is not bent into a part. TraceRecord carries the record's time; JourneyRun the run's finalTime. SceneProgram gains {kind: "clock", symbol, performer, advance} and a SceneVariant may carry its own program (programOf); the shell exposes program and summarizes a machine as "7 states, 7 transitions".
• The Debug panel is reused: each record line is prefixed with its clock instant; for a clocked scene the Send bar, the seed controls and the "Waiting events" line are hidden (data-osml-debug-events), and a scene-specific hint shows. The .is-live lighting now also applies to a machine's state boxes (osml-state).
• Snapshot editors/vscode/src/landing/phases.json is pinned by tests/wasm/landing_phases_test.go (TestLandingMissionPhasesModel), which also checks the view's states and transition labels, the mission's instantiation, and the two clocked runs the scene offers.
• Caption, editor hint and changelog fragment added.

Landing order with #1778 (feat/execute-action-trace-events, which adds trace/events to ExecuteAction): this PR lands first. A dry merge of #1778's head onto this branch conflicts in internal/exec/runtime/context.go, internal/frontend/engine/{engine,json}.go and internal/frontend/grpc/{run_options,service}.go; the resolution is mechanical and was built and tested locally (tests/wasm, tests/grpc, internal/frontend/grpc green on the merged tree): thread #1778's events []runtime.Message through ExecuteActionAdvancedBy/ActionOutcomeAdvancedBy/startActionAdvancedBy (calling DeliverEvents before Advance), keep both new JSON fields, and have runAction pick ExecuteActionWithEvents or ExecuteActionAdvancedBy by advance. #1778 should merge develop after this lands and apply that resolution; neither branch is rebased.

How it was verified

• tests/wasm/engine_advance_test.go: MissionSequence::MissionPhases performed by MissionSequence::mission with advance: 400000 answers statesVisited prelaunch, translunarCoast, lunarOrbit, onSurface, finalTime 400000 and transition records at t=9000, 279000, 379000; advance: 800000 reaches recovered then done at t=702000; without advance the machine runs through its clock to done at t=702000; every answer is byte-equal to the service's. An action run for 2 s stops short of its wait at t=5 and says so, run for 10 s completes; advance: -1 is refused as InvalidArgument on both methods.
• tests/wasm/landing_phases_test.go pins the scene's snapshot and the two clocked runs; editors/vscode unit tests cover machineModel, stateIdOf, runClock (performer/advance/trace on the wire, finalTime kept, a failed run's partial trace), programOf and the three-scene chooser.
• The existing gRPC conformance fixture execute_state_exhibited_performance_performer ("advance": 20) and the internal/frontend/grpc run-option tests stay green through the refactor.
• CLI cross-check: ./bin/sysml -quiet -instantiate MissionSequence::mission -state MissionSequence::mission -advance 400000 examples/runtime-showcase/mission-sequence.sysml ends in onSurface waiting on t=457000; -advance 800000 reports "State machine completed"; the engine answers the same states and instants.
• Local gates: go build ./..., go vet ./..., gofmt -l . (empty), go test ./... all packages ok (four heavy packages — cmd/sysml, internal/exec/runtime, internal/exec/smt, tests/codegen — hit the 10-minute timeout only while the browser run and the Node tests shared the machine, and passed re-run alone); staticcheck clean on the touched packages; cd editors/vscode && npm run build && npm run typecheck && npm test (449 pass, 0 fail); cd client/node && rm build/wasm/sysml-wasm.wasm && npm run build && npm test (471 pass, 0 fail, 1 skipped as on develop).
• Browser-verified on the built MkDocs site against the real wasm module (cache disabled): first paint from the snapshot (8 boxes, 7 transitions); Run ends with ExecuteState ran MissionPhases on mission for 400,000 s in 31 ms: prelaunch → translunarCoast → lunarOrbit → onSurface. The clock stopped at t = 400,000 s with the machine still in onSurface.; with the variant on, … → transEarthCoast → recovered → done. The clock stopped at t = 800,000 s; the machine completed when a transition reached done at t = 702,000 s.; the Debug panel steps the records with their instants; editing after 9000 [s] to 5000 redraws and the first transition reads t = 5,000 s; the stack and mass scenes still run; Download PNG saves mission-phases.png; no console errors beyond the theme's two api.github.com 403s.

400,000 s — stops in onSurface	800,000 s — reaches done

First paint from the snapshot	Debug panel with clock instants

Checklist

• make test and make lint pass locally
• Tests added or updated for the change
• Documentation extended where it already covers the surface (see CONTRIBUTING.md) — the hero's caption and hints are the documentation of the scene; the wire contract already documents advance
• Changelog entry added as changes/unreleased/<slug>.<section>.md, not as an edit to CHANGELOG.md
• baselines regenerated and make docs-counts run if a gate count moved (compliance rows need nothing: the census is counted at docs build) — no gate count moved
• No internal work-item labels (waves, slices, F4, K5) in the body, docs, or changelog

Link to Devin session: https://nasa-jpl-demo.devinenterprise.com/sessions/5da68ef994984c60bf6057a840223710
Open in Devin Desktop: https://nasa-jpl-demo.devinenterprise.com/desktop/session/5da68ef994984c60bf6057a840223710?variant=devin
Requested by: @HuiJun

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring