After the v7 import fixes (SciML#445) and docs fixes (SciML#448, SciML#449), several
Tests jobs hit `ExtraVariablesSystemException` from MTK 11's stricter
mtkcompile balance check. The dangling variables aren't bugs in the
test models — they're sensor / output connectors that the test never
consumes — so mark them as `outputs=` (excluded from the balance check)
or pass `fully_determined=false`:

- `test/Blocks/utils.jl` "SISO Check": `outputs = [so.output.u]`
- `test/Thermal/thermal.jl` "Heat flow system":
  `outputs = [mass1.T, hf_sensor2.port_b.Q_flow]`
- `test/Mechanical/rotational.jl` "sensors": `fully_determined=false`
  (11 dangling sensor variables make an `outputs=` listing impractical)
- `test/Mechanical/translational.jl` "AccelerationSensor":
  `mtkcompile(sys; fully_determined = false)`

Two further test failures are upstream-only and not addressed here:
- `test/Blocks/sources.jl` BSplineInterpolation / Initialization:
  SymbolicUtils `MethodError: fntype_X_Y(::Type{Real})` from
  `promote_symtype` when MTK substitutes through a callable parameter
  of a `ParametrizedInterpolation`. Needs a SymbolicUtils fix.
- `test/Blocks/test_analysis_points.jl` `get_looptransfer`: MTK
  initialization rejects with "Cyclic guesses detected" inside
  `varmap_to_vars`. Needs an MTK fix or explicit `missing_guess_value`.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

After the v7 import fixes (SciML#445) and docs fixes (SciML#448, SciML#449), several
Tests jobs hit `ExtraVariablesSystemException` from MTK 11's stricter
mtkcompile balance check. The dangling variables aren't bugs in the
test models — they're sensor / output connectors the test never feeds
back, so semantically they're outputs. Declare them via `outputs=` so
mtkcompile excludes them from the balance check (no `fully_determined=false`,
no skipped tests):

- `test/Blocks/utils.jl` "SISO Check": `outputs = [so.output.u]`.
- `test/Thermal/thermal.jl` "Heat flow system":
  `outputs = [mass1.T, hf_sensor2.port_b.Q_flow]`.
- `test/Mechanical/rotational.jl` "sensors": switch from `@mtkcompile`
  to `@named model = Sensors(); sys = mtkcompile(model; outputs = [...])`
  listing the 11 dangling sensor/connector variables.
- `test/Mechanical/translational.jl` "AccelerationSensor":
  `outputs = [mass.v, mass.flange.s]`.

Two further test failures remain on this PR (intentionally — not
disabled, not skipped) and are upstream-blocked:
- `test/Blocks/sources.jl` BSplineInterpolation / Initialization:
  SymbolicUtils `MethodError: fntype_X_Y(::Type{Real})` from
  `promote_symtype` when MTK substitutes through a callable parameter
  of a `ParametrizedInterpolation`. Root cause is in SymbolicUtils
  (and/or the `(interpolator::interp_type)(..)::eltype(u)` declaration
  in `src/Blocks/sources.jl`).
- `test/Blocks/test_analysis_points.jl` `get_looptransfer`: MTK
  initialization rejects with "Cyclic guesses detected" inside
  `varmap_to_vars`. Needs an MTK fix or an explicit
  `missing_guess_value`.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>