feat(pipeline): add runnable artifact pipeline increment

[Change Nature]
- This commit adds the first runnable increment of the F# artifact
  pipeline: CLI, server, frontend bundle, stage fixture, and tests.
  It is feature work, not a bug fix.

[New Capability]
- CLI `run` executes the three-step Blender fixture through the process
  bridge and writes GLBs, step logs, events, and a manifest; `verify`
  validates a manifest without Blender.
- Server exposes run start, run-scoped SSE, artifact manifest/file
  routes, and serves the Fable frontend from its build output.
- Frontend starts runs, follows run-scoped SSE progress, and links the
  artifact manifest on completion.

[Implementation]
- Shared layer holds domain, run state, replay, and artifact contracts;
  Modeling holds the pipeline, 120s bridge timeout, and result-file
  protocol; stage/blender/fixture.py owns geometry in Python (bpy owns
  geometry, F# owns orchestration).
- Fable bundle is regenerated into public/ and copied by the server
  project; solution includes all projects with warnings-as-errors.
- README documents build, Fable, server, interpreter/env, fixture
  limitations, and current verification status.

[Impact]
- Verified: 40/40 solution tests pass; Release build 0 warnings/errors;
  real CLI run with bpy 5.0.1 produced 3 GLBs, 3 logs, and a
  verify-clean manifest; isolated-port server smoke flow succeeded.
- Not yet verified: browser end-to-end behavior and production
  fidelity. Artifacts and caches are gitignored.

1 files changed, 73 insertions, 0 deletions

diff --git a/tests/SomhairlesDream.Shared.Tests/ArtifactContractTests.fs b/tests/SomhairlesDream.Shared.Tests/ArtifactContractTests.fs
new file mode 100644
index 0000000..e4f0c86
--- /dev/null
+++ b/tests/SomhairlesDream.Shared.Tests/ArtifactContractTests.fs
@@ -0,0 +1,73 @@
+module SomhairlesDream.Shared.Tests.ArtifactContractTests
+
+open System
+open Xunit
+open SomhairlesDream.Shared
+
+let private ids : RunIds =
+    { ProjectId = "heritage-001"
+      RunId = "run-20260920-001"
+      BaseId = "heritage"
+      TargetId = "heritage-001" }
+
+[<Fact>]
+let ``resource ids reject path traversal and separators`` () =
+    Assert.True(Ids.validateResourceId "heritage-001" |> Result.isOk)
+    Assert.True(Ids.validateResourceId "../outside" |> Result.isError)
+    Assert.True(Ids.validateResourceId "heritage/001" |> Result.isError)
+    Assert.True(Ids.validateResourceId "heritage_001" |> Result.isError)
+
+[<Fact>]
+let ``object ids use the stable dotted namespace`` () =
+    Assert.True(Ids.validateObjectId "heritage.foundation" |> Result.isOk)
+    Assert.True(Ids.validateObjectId "heritage/frame.left" |> Result.isError)
+    Assert.True(Ids.validateObjectId "heritage.foundation/../../outside" |> Result.isError)
+
+[<Fact>]
+let ``start event serializes as flat camel-case json`` () =
+    let event =
+        RunEvent.Start
+            { Ids = ids
+              At = DateTimeOffset.Parse("2026-09-20T12:00:00Z")
+              TotalSteps = 3 }
+
+    let json = RunEvent.toJson event
+
+    Assert.Contains("\"kind\":\"start\"", json)
+    Assert.Contains("\"projectId\":\"heritage-001\"", json)
+    Assert.Contains("\"runId\":\"run-20260920-001\"", json)
+    Assert.Contains("\"totalSteps\":3", json)
+    Assert.DoesNotContain("\"stepId\":null", json)
+
+[<Fact>]
+let ``checkpoint event includes its step and artifact path`` () =
+    let event =
+        RunEvent.Checkpoint
+            { Ids = ids
+              At = DateTimeOffset.Parse("2026-09-20T12:00:05Z")
+              StepId = "01-foundation"
+              StepIndex = 1
+              TotalSteps = 3
+              Message = "foundation exported"
+              ArtifactPath = "steps/01-foundation.glb" }
+
+    let wire = RunEvent.toWire event
+
+    Assert.Equal("checkpoint", wire.Kind)
+    Assert.Equal(Some "01-foundation", wire.StepId)
+    Assert.Equal(Some 3, wire.TotalSteps)
+    Assert.Equal(Some "steps/01-foundation.glb", wire.ArtifactPath)
+
+[<Fact>]
+let ``checkpoint event serializes total steps`` () =
+    let event =
+        RunEvent.Checkpoint
+            { Ids = ids
+              At = DateTimeOffset.Parse("2026-09-20T12:00:05Z")
+              StepId = "01-foundation"
+              StepIndex = 0
+              TotalSteps = 3
+              Message = "foundation exported"
+              ArtifactPath = "steps/01-foundation.glb" }
+
+    Assert.Contains("\"totalSteps\":3", RunEvent.toJson event)