ConfigBounds (students 10-500, edgesPerNode 1-8, forwardProb 0-0.9,
triangleProb 0-1) caps what RunScenario accepts: a student does not
keep 150 close friendships and a guaranteed forward is not a real
base rate. numEducated gains its missing upper limit (numStudents).
Bounds-side validation also protects the public server from absurd
numStudents values. GET /api/config/default now returns
{config, bounds} so the frontend can drive its controls from the
same numbers; the frontend does not call it yet, so this commit
changes no UI behaviour.
writeJSON's last-resort branch (json.Marshal failing, a programmer
error: unsupported type or cyclic data) previously fell back to
http.Error, which answers text/plain and was the one corner where the
API broke its own {"error": ...} contract. It now writes a
hand-written constant JSON literal: still strictly simpler than the
encoder that just failed (the reason writeError, which is built ON
writeJSON, cannot be used there: it would be circular), but contract
consistent. Tested by forcing the branch with a channel payload,
which json.Marshal cannot encode.
internal/api stays a translation layer: decode (with
DisallowUnknownFields so typos 400 instead of silently defaulting),
run the engine, encode; all validation stays in the engine. Routes use
Go 1.22 mux patterns ('POST /api/comparison'), so wrong methods get
405 from the stdlib for free. httptest runs handlers fully in memory;
the API test re-pins the 99/70/7 golden values end to end.
ComparisonResponse is added to tygo.yaml with a type mapping so the
generated web/src/types/api.ts reuses the engine's TS types.
cmd/spreadlab now serves on -addr (default localhost:8080); -table
keeps the CLI comparison as a sanity check.
