test: cap dt in the marginal continuous-callback crossing-time tests

The three `solve(prob, Tsit5())` calls in "Additional
SymbolicContinuousCallback options" assert event times to 1.0e-4 while
integrating at the default `reltol = 1.0e-3`. For `c2 = cos(3t)` that
leaves no room: the numerical trajectory carries ~2e-4 of error, and
since `dc2/dt = ±3` at the crossings the recorded event time inherits
~7e-5 of it -- a 1.4x margin against the assertion. The rootfind itself
is exact (the condition value at the recorded time is ~1e-16), so what
these tests actually measured was default-tolerance quadrature error,
not event handling.

OrdinaryDiffEqCore 4.12.0 (SciML/OrdinaryDiffEq.jl#3720) reinitializes
the step-size controller after any continuous callback with
`maybe_discontinuity = true`, which is correct -- a PI controller's
history is meaningless across a discontinuity -- but it changes the step
sequence, and the c2 error grew to ~8e-4, pushing the crossing times to
2.6e-4 and over the threshold.

Pass `dtmax = 0.01` as the other four solves in the same testset already
do. Crossing times land within ~1e-12, so the assertions now test the
rootfind rather than the controller.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TNqmRywBbj51czPQgoiEC7

Author: ChrisRackauckas

lib/ModelingToolkitBase/test/symbolic_events.jl

@@ -722,7 +722,7 @@ end
     @named trigsys = System(eqs, t; continuous_events = [evt1, evt2])
     trigsys_ss = mtkcompile(trigsys)
     prob = ODEProblem(trigsys_ss, [], (0.0, 2π))
-    sol = solve(prob, Tsit5())
+    sol = solve(prob, Tsit5(); dtmax = 0.01)
     required_crossings_c1 = [π / 2, 3 * π / 2]
     required_crossings_c2 = [π / 6, π / 2, 5 * π / 6, 7 * π / 6, 3 * π / 2, 11 * π / 6]
     @test maximum(abs.(first.(cr1) .- required_crossings_c1)) < 1.0e-4
@@ -841,7 +841,7 @@ end
     @named trigsys = System(eqs, t; continuous_events = [evt1, evt2])
     trigsys_ss = mtkcompile(trigsys)
     prob = ODEProblem(trigsys_ss, [], (0.0, 2π))
-    sol = solve(prob, Tsit5())
+    sol = solve(prob, Tsit5(); dtmax = 0.01)
     @test maximum(abs.(first.(cr1) .- required_crossings_c1)) < 1.0e-4
     @test maximum(abs.(first.(cr2) .- required_crossings_c2)) < 1.0e-4
     @test sign.(cos.(required_crossings_c1 .- 1.0e-6)) == sign.(last.(cr1))
@@ -861,7 +861,7 @@ end
     @named trigsys = System(eqs, t; continuous_events = [evt2, evt1])
     trigsys_ss = mtkcompile(trigsys)
     prob = ODEProblem(trigsys_ss, [], (0.0, 2π))
-    sol = solve(prob, Tsit5())
+    sol = solve(prob, Tsit5(); dtmax = 0.01)
     @test maximum(abs.(first.(cr1) .- required_crossings_c1)) < 1.0e-4
     @test maximum(abs.(first.(cr2) .- required_crossings_c2)) < 1.0e-4
     @test sign.(cos.(required_crossings_c1 .- 1.0e-6)) == sign.(last.(cr1))