Step 11: deterministic pathfinding and authoritative movement

[MerverliPy]

Status

Step 11 implementation continues from validated Step 10 main (f6be88e0c7c273899263661e31fb6c9639b006f8).

Implemented in this draft

• deterministic cardinal breadth-first pathfinding
• canonical MapCellId tie-breaking independent of registration/insertion order
• blocked-cell and blocked-destination handling
• deterministic re-path behavior after obstruction changes
• 100-route concurrent stress test
• canonical movement-agent entity component state
• canonical movement serialization and checksum writer
• deterministic one-cell authoritative movement planner
• expanded harness from 72 to 78 registered tests

The movement component intentionally uses the existing entity component registration, persistence, and entity-checksum mechanisms. No parallel world, persistence, or checksum system was introduced.

Still required before completion

• buffered movement replacement mutation through the existing Commit phase
• commit visibility/conflict tests
• full save/load continuity test using movement entities
• global/component checksum divergence test
• replay and frame-pattern equivalence
• obstruction-churn soak coverage
• Release build and exact owner validation evidence
• backup/rollback artifacts

Closes #1 only after every completion gate is satisfied. This PR remains draft and must not be merged before owner validation.

[Copilot]

Pull request overview

Implements Step 11’s deterministic, cardinal BFS pathfinding and a minimal authoritative movement loop backed by a canonical MovementAgentState component, integrated into the existing mutation/Commit + persistence + checksum + replay pipelines (including new validation workflow and expanded milestone tests).

Changes:

• Added deterministic BFS pathfinding with canonical neighbor tie-breaking and blocked-cell/destination handling.
• Introduced authoritative movement state (MovementAgentState) plus a one-cell-per-plan movement planner.
• Added component replacement support via the existing mutation/Commit pipeline and expanded the exact harness with Step 11 milestone, save/load, replay, frame-pattern, and soak tests.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
GenerationArk.Simulation/State/MutationBuffer.cs	Adds EnqueueReplace and Commit/validation/conflict handling for ReplaceComponent.
GenerationArk.Simulation/State/EntityMutationKind.cs	Introduces ReplaceComponent = 5 while preserving existing enum values.
GenerationArk.Simulation/State/ComponentStore.cs	Adds Replace to update an existing component value for an entity.
GenerationArk.Simulation/State/ComponentRegistry.cs	Adds registry-level Replace wiring with entity/type checks.
GenerationArk.Simulation/Movement/MovementAgentState.cs	Defines canonical movement component registration, serialization, and checksum participation.
GenerationArk.Simulation/Movement/DeterministicPathfinder.cs	Implements deterministic cardinal BFS with canonical neighbor ordering.
GenerationArk.Simulation/Movement/AuthoritativeMovementPlanner.cs	Implements deterministic one-step authoritative movement planning.
GenerationArk.Simulation.Tests/Step11WorkflowTrigger.cs	Adds a behavior-neutral CI trigger marker.
GenerationArk.Simulation.Tests/Program.cs	Registers new Step 11 milestone tests in the exact harness.
GenerationArk.Simulation.Tests/PathfindingMilestoneTests.cs	Adds deterministic pathfinding + movement state + planner milestone tests (incl. 100-route concurrency).
GenerationArk.Simulation.Tests/MovementSaveLoadContinuityTests.cs	Adds movement save/load continuity and checksum equivalence coverage using the existing snapshot pipeline.
GenerationArk.Simulation.Tests/MovementReplayEquivalenceTests.cs	Adds replay, frame-pattern equivalence, and long soak determinism checks for movement scenarios.
GenerationArk.Simulation.Tests/ComponentReplacementMilestoneTests.cs	Adds replacement invisibility/atomic conflict rejection/checksum-change tests.
GenerationArk.Simulation.Tests/ArrayEnumerableExtensions.cs	Adds an array Reverse() extension delegating to LINQ to avoid span/in-place overload resolution pitfalls in tests.
Generation-Ark-Session-Handoff-Step11-Movement-Core-CI-Validated.md	Adds a Step 11 status/handoff artifact documenting CI validation and next gates.
.github/workflows/step11-validation.yml	Adds Step 11 CI workflow (Release build + exact harness) with build log artifact upload.

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