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, 218 insertions, 0 deletions

diff --git a/src/SomhairlesDream.Shared/Artifact.fs b/src/SomhairlesDream.Shared/Artifact.fs
new file mode 100644
index 0000000..d1cb4f0
--- /dev/null
+++ b/src/SomhairlesDream.Shared/Artifact.fs
@@ -0,0 +1,218 @@
+namespace SomhairlesDream.Shared
+
+open System
+#if !FABLE_COMPILER
+open System.Text.Json
+open System.Text.Json.Nodes
+#endif
+
+[<CLIMutable>]
+type RunIds =
+    { ProjectId: string
+      RunId: string
+      BaseId: string
+      TargetId: string }
+
+module Ids =
+    open System.Text.RegularExpressions
+
+    let private resourcePattern = Regex("^[a-z0-9](?:[a-z0-9-]{0,62}[a-z0-9])?$", RegexOptions.CultureInvariant)
+    let private objectPattern = Regex("^[a-z0-9]+(?:[._-][a-z0-9]+)*$", RegexOptions.CultureInvariant)
+
+    let validateResourceId value =
+        if isNull value || not (resourcePattern.IsMatch(value)) then
+            Error "resource id must contain only lower-case letters, digits, and hyphens"
+        else
+            Ok ()
+
+    let validateObjectId value =
+        if isNull value || not (objectPattern.IsMatch(value)) then
+            Error "object id must use the dotted lower-case namespace"
+        else
+            Ok ()
+
+[<CLIMutable>]
+type RunStart =
+    { Ids: RunIds
+      At: DateTimeOffset
+      TotalSteps: int }
+
+[<CLIMutable>]
+type RunHeartbeat =
+    { Ids: RunIds
+      At: DateTimeOffset
+      Message: string }
+
+[<CLIMutable>]
+type RunCheckpoint =
+    { Ids: RunIds
+      At: DateTimeOffset
+      StepId: string
+      StepIndex: int
+      TotalSteps: int
+      Message: string
+      ArtifactPath: string }
+
+[<CLIMutable>]
+type RunComplete =
+    { Ids: RunIds
+      At: DateTimeOffset
+      ManifestPath: string }
+
+[<CLIMutable>]
+type RunFail =
+    { Ids: RunIds
+      At: DateTimeOffset
+      StepId: string option
+      Message: string }
+
+type RunEvent =
+    | Start of RunStart
+    | Heartbeat of RunHeartbeat
+    | Checkpoint of RunCheckpoint
+    | Complete of RunComplete
+    | Fail of RunFail
+
+[<CLIMutable>]
+type RunEventWire =
+    { Kind: string
+      At: DateTimeOffset
+      ProjectId: string
+      RunId: string
+      BaseId: string
+      TargetId: string
+      TotalSteps: int option
+      StepId: string option
+      StepIndex: int option
+      Message: string option
+      ArtifactPath: string option
+      ManifestPath: string option }
+
+module RunEvent =
+    let private ids (value: RunIds) =
+        value.ProjectId, value.RunId, value.BaseId, value.TargetId
+
+    let toWire event =
+        let kind, eventIds, at, totalSteps, stepId, stepIndex, message, artifactPath, manifestPath =
+            match event with
+            | Start value ->
+                "start", value.Ids, value.At, Some value.TotalSteps, None, None, None, None, None
+            | Heartbeat value ->
+                "heartbeat", value.Ids, value.At, None, None, None, Some value.Message, None, None
+            | Checkpoint value ->
+                "checkpoint",
+                value.Ids,
+                value.At,
+                Some value.TotalSteps,
+                Some value.StepId,
+                Some value.StepIndex,
+                Some value.Message,
+                Some value.ArtifactPath,
+                None
+            | Complete value ->
+                "complete", value.Ids, value.At, None, None, None, None, None, Some value.ManifestPath
+            | Fail value ->
+                "fail", value.Ids, value.At, None, value.StepId, None, Some value.Message, None, None
+
+        let projectId, runId, baseId, targetId = ids eventIds
+
+        { Kind = kind
+          At = at
+          ProjectId = projectId
+          RunId = runId
+          BaseId = baseId
+          TargetId = targetId
+          TotalSteps = totalSteps
+          StepId = stepId
+          StepIndex = stepIndex
+          Message = message
+          ArtifactPath = artifactPath
+          ManifestPath = manifestPath }
+
+#if !FABLE_COMPILER
+    let private addOptional (json: JsonObject) (name: string) value create =
+        match value with
+        | Some item -> json[name] <- create item
+        | None -> ()
+
+    let private jsonOptions () =
+        let options = JsonSerializerOptions()
+        options.PropertyNamingPolicy <- JsonNamingPolicy.CamelCase
+        options.WriteIndented <- false
+        options
+
+    let toJson event =
+        let wire = toWire event
+        let json = JsonObject()
+        json["kind"] <- JsonValue.Create(wire.Kind)
+        json["at"] <- JsonValue.Create(wire.At)
+        json["projectId"] <- JsonValue.Create(wire.ProjectId)
+        json["runId"] <- JsonValue.Create(wire.RunId)
+        json["baseId"] <- JsonValue.Create(wire.BaseId)
+        json["targetId"] <- JsonValue.Create(wire.TargetId)
+        addOptional json "totalSteps" wire.TotalSteps (fun value -> JsonValue.Create(value))
+        addOptional json "stepId" wire.StepId (fun value -> JsonValue.Create(value))
+        addOptional json "stepIndex" wire.StepIndex (fun value -> JsonValue.Create(value))
+        addOptional json "message" wire.Message (fun value -> JsonValue.Create(value))
+        addOptional json "artifactPath" wire.ArtifactPath (fun value -> JsonValue.Create(value))
+        addOptional json "manifestPath" wire.ManifestPath (fun value -> JsonValue.Create(value))
+        json.ToJsonString(jsonOptions())
+#endif
+
+[<CLIMutable>]
+type ArtifactChange =
+    { ObjectId: string
+      Kind: string
+      Summary: string }
+
+[<CLIMutable>]
+type RenderArtifact =
+    { ArtifactPath: string
+      Sha256: string
+      Bytes: int64
+      ExportedAt: DateTimeOffset }
+
+[<CLIMutable>]
+type StepArtifact =
+    { StepId: string
+      StepIndex: int
+      ArtifactPath: string
+      LogPath: string
+      Sha256: string
+      Bytes: int64
+      ExportedAt: DateTimeOffset
+      ObjectIds: string array
+      VerifiedObjectIds: string array
+      Changes: ArtifactChange array
+      Render: RenderArtifact option }
+
+[<CLIMutable>]
+type ArtifactManifest =
+    { SchemaVersion: int
+      ProjectId: string
+      RunId: string
+      BaseId: string
+      TargetId: string
+      Status: string
+      StartedAt: DateTimeOffset
+      CompletedAt: DateTimeOffset
+      BlenderVersion: string
+      Steps: StepArtifact array }
+
+[<CLIMutable>]
+type RunSnapshot =
+    { ProjectId: string
+      RunId: string
+      BaseId: string
+      TargetId: string
+      Status: string
+      CurrentStepId: string option
+      CurrentStepIndex: int
+      TotalSteps: int
+      LastHeartbeatAt: DateTimeOffset option
+      UpdatedAt: DateTimeOffset
+      Message: string
+      ManifestPath: string option
+      ManifestUrl: string option
+      Error: string option
+      IsStale: bool }