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, 31 insertions, 0 deletions

diff --git a/src/SomhairlesDream.Modeling/Definitions.fs b/src/SomhairlesDream.Modeling/Definitions.fs
new file mode 100644
index 0000000..64e6bc6
--- /dev/null
+++ b/src/SomhairlesDream.Modeling/Definitions.fs
@@ -0,0 +1,31 @@
+namespace SomhairlesDream.Modeling
+
+open SomhairlesDream.Shared
+
+[<CLIMutable>]
+type DesignStep =
+    { StepId: string
+      Index: int
+      ObjectIds: string array
+      Changes: ArtifactChange array }
+
+module Design =
+    let steps : DesignStep array =
+        [| { StepId = "01-foundation"; Index = 0
+             ObjectIds = [| "heritage.foundation"; "heritage.deck" |]
+             Changes =
+                 [| { ObjectId = "heritage.foundation"; Kind = "add"; Summary = "Add foundation slab" }
+                    { ObjectId = "heritage.deck"; Kind = "add"; Summary = "Add raised deck" } |] }
+           { StepId = "02-frame"; Index = 1
+             ObjectIds =
+                 [| "heritage.foundation"; "heritage.deck"; "heritage.frame.left"; "heritage.frame.right"; "heritage.spine" |]
+             Changes =
+                 [| { ObjectId = "heritage.frame.left"; Kind = "add"; Summary = "Add primary left frame" }
+                    { ObjectId = "heritage.frame.right"; Kind = "add"; Summary = "Add primary right frame" }
+                    { ObjectId = "heritage.spine"; Kind = "add"; Summary = "Add central spine" } |] }
+           { StepId = "03-cabin"; Index = 2
+             ObjectIds =
+                 [| "heritage.foundation"; "heritage.deck"; "heritage.frame.left"; "heritage.frame.right"; "heritage.spine"; "heritage.cabin"; "heritage.crossbeam" |]
+             Changes =
+                 [| { ObjectId = "heritage.cabin"; Kind = "add"; Summary = "Add cabin volume" }
+                    { ObjectId = "heritage.crossbeam"; Kind = "add"; Summary = "Add cabin crossbeam" } |] } |]