Step 11: deterministic pathfinding and authoritative movement

.github/workflows/step11-validation.yml

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+name: Step 11 Validation
+
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - step11/deterministic-pathfinding-movement
+
+permissions:
+  contents: read
+
+jobs:
+  release-validation:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup .NET 8
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 8.0.x
+
+      - name: Restore
+        run: dotnet restore GenerationArk.Simulation.Tests/GenerationArk.Simulation.Tests.csproj --verbosity quiet
+
+      - name: Build Release
+        id: build
+        shell: bash
+        run: |
+          set +e
+          dotnet build GenerationArk.Simulation.Tests/GenerationArk.Simulation.Tests.csproj --configuration Release --no-restore --verbosity minimal > step11-build.log 2>&1
+          status=$?
+          cat step11-build.log
+          exit $status
+
+      - name: Upload build diagnostics
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: step11-build-diagnostics
+          path: step11-build.log
+          if-no-files-found: error
+
+      - name: Run exact harness
+        run: dotnet run --project GenerationArk.Simulation.Tests/GenerationArk.Simulation.Tests.csproj --configuration Release --no-build

Generation-Ark-Session-Handoff-Step11-Movement-Core-CI-Validated.md

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+# Generation Ark — Session Handoff: Step 11 Movement Core CI Validated
+
+## Status
+
+Step 11 movement-core implementation is active on a draft pull request. The current branch has a successful Release build and an exact 81/81 test-harness result in GitHub Actions. Movement persistence, replay continuity, frame-pattern equivalence, dynamic-obstruction soak, and owner validation are not yet complete.
+
+This file is the authoritative baseline for the next Step 11 phase.
+
+## Repository and branch
+
+- Repository: `MerverliPy/Generation-Ark`
+- Base branch: `main`
+- Active branch: `step11/deterministic-pathfinding-movement`
+- Draft pull request: `#3`
+- Validated branch head: `9badf518f0b12c875ccb7642d510593b548fa1a5`
+- Step 10 validated main commit: `f6be88e0c7c273899263661e31fb6c9639b006f8`
+- Step 10 source commit: `03ac1cfd8cab11011c205bedf4ee3bae88265784`
+
+## Validation evidence
+
+- Workflow: `Step 11 Validation`
+- Workflow run: `29697124585`
+- Job: `release-validation`
+- Restore: passed
+- Release build: passed
+- Warnings-as-errors gate: passed
+- Exact console harness: passed
+- Test result: `81/81`
+- Runner OS: Ubuntu 24.04
+- Target framework: .NET 8
+
+The pull request must remain draft and unmerged until all remaining Step 11 gates and owner validation are complete.
+
+## Preserved backup
+
+Do not remove or overwrite:
+
+`/home/calvin/Generation-Ark/generation-ark-clock-before-git-sync-20260719T164917Z.tar.gz`
+
+## Completed Step 11 movement core
+
+### Deterministic pathfinding
+
+- Deterministic cardinal pathfinding is implemented.
+- Neighbor traversal and tie-breaking use canonical `MapCellId` ordering.
+- Blocked cells are avoided.
+- Blocked destinations fail deterministically.
+- Repathing after obstruction changes is deterministic.
+- A 100-agent concurrent-route test is registered and passing.
+
+### Movement state
+
+`MovementAgentState` is the authoritative movement component and includes:
+
+- current cell
+- destination cell
+- movement revision
+- canonical registration
+- canonical serialization and deserialization
+- checksum participation
+
+### Movement planning
+
+`AuthoritativeMovementPlanner`:
+
+- advances exactly one canonical cell per planning call
+- does not mutate authoritative world state directly
+- produces Commit-bound replacement intent
+- reuses the existing world, mutation, Commit, save, replay, and checksum architecture
+
+## Component replacement infrastructure
+
+Replacement support was added to the existing component and mutation pipeline.
+
+### Component store
+
+`ComponentStore.Replace(EntityId, object)`:
+
+- rejects null values
+- requires the exact registered runtime type
+- requires the component to already exist
+- replaces the stored value without changing component identity
+
+### Component registry
+
+`ComponentRegistry.Replace(EntityRegistry, EntityId, ComponentValue)`:
+
+- validates arguments
+- requires the entity to exist
+- delegates to the registered component store
+
+### Mutation kind
+
+`EntityMutationKind.ReplaceComponent = 5`
+
+Existing enum numeric values were preserved:
+
+- `CreateEntity = 1`
+- `DestroyEntity = 2`
+- `AddComponent = 3`
+- `RemoveComponent = 4`
+- `ReplaceComponent = 5`
+
+### Mutation buffer semantics
+
+`MutationBuffer` now supports `EnqueueReplace` and applies replacements through the existing Commit path.
+
+Validation requires:
+
+- the entity exists
+- the component type is registered
+- the replacement runtime type exactly matches the registration
+- the entity already owns the component
+
+Conflict rules reject atomically:
+
+- replace + replace for the same entity/component
+- add + replace for the same entity/component
+- remove + replace for the same entity/component
+- destroy + replace for the same entity
+- any multiple structural component mutations targeting the same entity/component in one batch
+
+Replacement remains invisible until Commit.
+
+## Focused replacement tests
+
+The following tests are registered and passing:
+
+- `ReplacementRemainsInvisibleUntilCommitAndThenApplies`
+- `ConflictingReplacementsRejectAtomically`
+- `MovementReplacementChangesCanonicalChecksum`
+
+The checksum test compares states at the same tick so divergence is attributable to movement state rather than clock state.
+
+## CI infrastructure
+
+`.github/workflows/step11-validation.yml` runs on the Step 11 branch and pull request.
+
+It performs:
+
+1. checkout
+2. .NET 8 setup
+3. restore
+4. Release build
+5. build-diagnostics artifact upload
+6. exact console harness execution
+
+The workflow preserves the real build exit status and uploads `step11-build.log` even when compilation fails.
+
+A small test-namespace array `Reverse` extension delegates explicitly to LINQ to avoid .NET array overload resolution selecting the in-place `void` overload in existing map tests.
+
+## Current test count
+
+The authoritative registered test count is:
+
+`81/81`
+
+This supersedes the Step 10 `72/72` baseline for the active Step 11 branch only. It does not complete Step 11.
+
+## Next authoritative work: movement persistence and replay continuity
+
+Continue from validated head `9badf518f0b12c875ccb7642d510593b548fa1a5`.
+
+Implement and validate movement continuity through the existing persistence and replay pipelines. Do not create parallel infrastructure.
+
+Required next gates:
+
+### 1. Save/load continuity
+
+- Persist `MovementAgentState` through the existing entity/component snapshot pipeline.
+- Restore authoritative current cell, destination, and revision exactly.
+- Verify canonical serialized bytes or canonical restored state.
+- Verify uninterrupted execution and save/load-resumed execution produce identical final checksums.
+
+### 2. Replay equivalence
+
+- Record movement-driving commands or deterministic movement inputs through the existing replay log.
+- Re-run from the same seed and initial state.
+- Verify checkpoint and final checksum equivalence.
+- Ensure replacement mutation sequencing remains stable across replay.
+
+### 3. Frame-pattern equivalence
+
+- Run the same movement scenario under multiple frame budgets and frame patterns.
+- Verify identical tick outcomes, movement positions, revisions, and canonical checksums.
+- Confirm no frame-rate-dependent path planning or movement advancement exists.
+
+### 4. Dynamic-obstruction deterministic soak
+
+- Include at least 100 concurrently moving agents.
+- Apply deterministic obstruction changes over a long run.
+- Require deterministic repathing and completion/failure behavior.
+- Compare repeated runs and varied frame patterns.
+- Retain bounded checkpoints.
+- Verify final checksum equivalence.
+
+### 5. Owner validation
+
+After CI is green for all Step 11 gates, owner validation must still produce retained evidence showing:
+
+- exact branch and commit SHA
+- .NET SDK version
+- Release build result
+- zero warnings and zero errors
+- exact final test count
+- soak and continuity evidence
+- backup preservation
+
+Do not mark the PR ready, merge it, close issue `#1`, or claim Step 11 complete before owner evidence exists.
+
+## Explicit exclusions
+
+Do not begin or introduce:
+
+- jobs or toils
+- reservation systems
+- needs or routines
+- atmosphere simulation
+- Unity presentation work
+- a second simulation runner
+- a second simulation clock
+- a second world root
+- a parallel Commit pipeline
+- a parallel save/load format
+- a parallel checksum pipeline
+
+## Guardrails
+
+- Preserve deterministic ordering everywhere.
+- Preserve all existing enum numeric values.
+- Preserve the Step 10 validated behavior and tests.
+- Reuse the existing mutation, Commit, persistence, replay, scheduler, and checksum systems.
+- Treat GitHub CI as development evidence, not owner validation.
+- Keep PR #3 draft and unmerged until every remaining gate passes.
+- Keep the preserved backup intact.
+
+## Immediate next step
+
+Add movement save/load continuity tests and the minimum persistence integration needed to make them pass. Then run the existing `Step 11 Validation` workflow and act only on concrete build or test evidence.

GenerationArk.Simulation.Tests/ArrayEnumerableExtensions.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace GenerationArk.Simulation.Tests;
+
+internal static class ArrayEnumerableExtensions
+{
+    public static IEnumerable<T> Reverse<T>(this T[] source)
+    {
+        ArgumentNullException.ThrowIfNull(source);
+        return Enumerable.Reverse(source);
+    }
+}