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, 72 insertions, 0 deletions

diff --git a/tests/SomhairlesDream.Modeling.Tests/BridgeTests.fs b/tests/SomhairlesDream.Modeling.Tests/BridgeTests.fs
new file mode 100644
index 0000000..d9c7347
--- /dev/null
+++ b/tests/SomhairlesDream.Modeling.Tests/BridgeTests.fs
@@ -0,0 +1,72 @@
+module SomhairlesDream.Modeling.Tests.BridgeTests
+
+open System
+open System.IO
+open Xunit
+open SomhairlesDream.Modeling
+
+let private withTempDirectory action =
+    let path = Path.Combine(Path.GetTempPath(), "somhairles-dream-bridge-" + Guid.NewGuid().ToString("N"))
+    Directory.CreateDirectory(path) |> ignore
+
+    try
+        action path
+    finally
+        if Directory.Exists(path) then
+            Directory.Delete(path, true)
+
+let private fixtureScript =
+    [| "import argparse"
+       "import json"
+       "import os"
+       ""
+       "parser = argparse.ArgumentParser()"
+       "parser.add_argument('--step-id', required=True)"
+       "parser.add_argument('--output', required=True)"
+       "parser.add_argument('--render-output')"
+       "parser.add_argument('--result-output')"
+       "args = parser.parse_args()"
+       "os.makedirs(os.path.dirname(args.output), exist_ok=True)"
+       "with open(args.output, 'wb') as stream:"
+       "    stream.write(b'glTF')"
+       "result_path = args.result_output or args.output + '.result.json'"
+       "with open(result_path, 'w', encoding='utf-8') as stream:"
+       "    json.dump({"
+       "        'ok': True,"
+       "        'blenderVersion': 'test',"
+       "        'exportedAt': '2026-09-20T12:00:05Z',"
+       "        'objectIds': ['heritage.foundation', 'heritage.deck'],"
+       "        'verifiedObjectIds': ['heritage.foundation', 'heritage.deck'],"
+       "        'glbBytes': 4"
+       "    }, stream)"
+       "with open(args.output + '.log', 'w', encoding='utf-8') as stream:"
+       "    stream.write('fixture log retained separately\\n')"
+       "print('Blender informational output')" |]
+    |> String.concat Environment.NewLine
+
+[<Fact>]
+let ``bridge reads result file instead of polluted stdout and retains process log`` () =
+    withTempDirectory (fun root ->
+        let blenderRoot = Path.Combine(root, "stage", "blender")
+        Directory.CreateDirectory(blenderRoot) |> ignore
+        File.WriteAllText(Path.Combine(blenderRoot, "fixture.py"), fixtureScript)
+
+        let output = Path.Combine(root, "run", "step.glb")
+        let request =
+            { Step = Design.steps[0]
+              GlbPath = output
+              RenderPath = None
+              ResultPath = output + ".result.json"
+              LogPath = output + ".log" }
+
+        let result =
+            (BlenderProcessBridge("python3", Path.Combine(root, "stage")) :> IArtifactBridge)
+                .Export(request, ignore)
+
+        match result with
+        | Error message -> failwith message
+        | Ok value ->
+            Assert.Equal("test", value.BlenderVersion)
+            Assert.Equal(4L, value.GlbBytes)
+            Assert.True(File.Exists(output + ".log"))
+            Assert.Contains("Blender informational output", File.ReadAllText(output + ".log")))