feat: add gds-control — state-space control DSL over GDS

[rororowyourboat]

Summary

• Adds gds-control package: state-space control DSL that compiles to GDSSpec/SystemIR
• Third independent DSL (after stockflow and games) validating GDS as a universal compositional substrate
• Maps classical (A,B,C,D) state-space form to canonical (X,U,g,f) decomposition
• All non-state-updating blocks use Policy — no ControlAction — preserving clean canonical structure
• 4 semantic spaces (State, Reference, Measurement, Control), 6 verification checks (CS-001..CS-006)
• Cross-built equivalence tests (double integrator) at Spec, Canonical, and SystemIR levels
• Parametric canonical invariants across 3 archetypes (tiny/medium/large)
• 117 new tests, zero regressions on gds-framework (373) and gds-stockflow (215)

Test plan

• uv run --package gds-control pytest packages/gds-control/tests -v — 117 passed
• uv run --package gds-framework pytest packages/gds-framework/tests -v — 373 passed (regression)
• uv run --package gds-stockflow pytest packages/gds-stockflow/tests -v — 215 passed (regression)
• uv run ruff check packages/gds-control/ — clean
• uv run ruff format --check packages/gds-control/ — clean

[Copilot]

Pull request overview

This PR adds gds-control, the third independent DSL for the GDS framework (alongside gds-stockflow and gds-games). It provides a declarative state-space control system DSL that compiles to GDSSpec and SystemIR, demonstrating GDS as a universal compositional substrate for control theory.

The package maps classical state-space control theory (A,B,C,D) matrices to the canonical GDS decomposition (X,U,g,f), where states become Mechanisms with Entity state variables, sensors and controllers become Policy blocks, and inputs become BoundaryActions. The design introduces four semantic spaces (State, Reference, Measurement, Control) with six domain-specific verification checks (CS-001 through CS-006).

Changes:

• Adds complete gds-control package with DSL elements, compilation to GDSSpec/SystemIR, and verification system
• Integrates package into workspace via root pyproject.toml dependencies and ruff configuration
• Provides 117 comprehensive tests covering element construction, model validation, compilation, state-space correspondence, and verification checks

Reviewed changes

Copilot reviewed 18 out of 21 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pyproject.toml	Adds gds-control to workspace dependencies and known-first-party imports
packages/gds-control/pyproject.toml	Package metadata, dependencies, and build configuration
packages/gds-control/README.md	Minimal package description linking to GDS ecosystem
packages/gds-control/CLAUDE.md	Comprehensive architecture and convention documentation
packages/gds-control/gds_control/init.py	Public API exports for DSL, compilation, and verification
packages/gds-control/gds_control/dsl/types.py	ElementType enum for control system categories
packages/gds-control/gds_control/dsl/errors.py	Domain-specific exceptions (CSError, CSValidationError, CSCompilationError)
packages/gds-control/gds_control/dsl/elements.py	Frozen Pydantic models for State, Input, Sensor, Controller
packages/gds-control/gds_control/dsl/model.py	ControlModel with construction-time validation and compilation methods
packages/gds-control/gds_control/dsl/compile.py	Compiler mapping ControlModel to GDSSpec and SystemIR with composition tree building
packages/gds-control/gds_control/verification/checks.py	Six domain-specific verification checks (CS-001 through CS-006)
packages/gds-control/gds_control/verification/engine.py	Verification orchestration running CS checks and optional GDS checks
packages/gds-control/tests/test_elements.py	Tests for element construction, defaults, and frozen behavior
packages/gds-control/tests/test_model.py	Tests for model validation with valid and invalid configurations
packages/gds-control/tests/test_compile.py	Tests for GDSSpec registration and SystemIR compilation
packages/gds-control/tests/test_state_space.py	Comprehensive cross-built equivalence tests and canonical invariants
packages/gds-control/tests/test_integration.py	End-to-end integration tests for SISO, MIMO, and open-loop systems
packages/gds-control/tests/test_verification.py	Tests for all six CS verification checks

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[Copilot]

Unreachable code detected. This return statement can never be executed because:

1. ControlModel validation requires at least one state
2. If state_blocks is non-empty (which it always will be), it gets added to tiers at line 277
3. Therefore tiers can never be empty at line 279

This code should be removed.

Suggested change

	if not tiers:
	return _parallel_tier(state_blocks)