refactor(producer): migrate test imports to render/shared.ts, drop re-export

Three small follow-ups on the shared.ts extraction, addressing review
feedback on #720:

- Hoist `BROWSER_MEDIA_EPSILON` from `probeStage.ts` into `shared.ts`
  so any future stage that reconciles browser media (chunked rendering
  re-probe, for instance) doesn't have to redeclare it.
- Migrate `renderOrchestrator.test.ts` to import the five moved symbols
  (`applyRenderModeHints`, `projectBrowserEndToCompositionTimeline`,
  `resolveDeviceScaleFactor`, `writeCompiledArtifacts`,
  `CompositionMetadata`) directly from `./render/shared.js`. This is
  the clean end state — the back-compat re-export through
  `renderOrchestrator.ts` was a stepping-stone.
- Drop the back-compat re-export block from `renderOrchestrator.ts`.
  No remaining importers go through it (verified via grep across
  `packages/`). The five symbols now have exactly one path:
  `./render/shared.js`.

No behavior change. Renderer smoke-tested inside `Dockerfile.test`
against `font-variant-numeric`, `many-cuts`, and `variables-prod` —
audio correlations 1.000 / 0.994 / 0.975, matching every prior PR in
the stack.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/producer/src/services/render/shared.ts

@@ -27,6 +27,14 @@ export interface CompositionMetadata {
   height: number;
 }
 
+/**
+ * Floating-point tolerance for reconciling browser-discovered media timing
+ * against statically-parsed metadata. Used when the browser reports a
+ * slightly different `end` / `mediaStart` / `volume` than the compiled
+ * HTML and we want to ignore sub-millisecond float noise.
+ */
+export const BROWSER_MEDIA_EPSILON = 0.0001;
+
 /**
  * Browser-discovered media inside inlined sub-compositions can still report
  * scene-local timing from the merged DOM (e.g. start=0, end=85.52) while the

packages/producer/src/services/render/stages/probeStage.ts

@@ -44,14 +44,13 @@ import {
 import { createFileServer, type FileServerHandle, VIRTUAL_TIME_SHIM } from "../../fileServer.js";
 import type { ProducerLogger } from "../../../logger.js";
 import {
+  BROWSER_MEDIA_EPSILON,
   projectBrowserEndToCompositionTimeline,
   writeCompiledArtifacts,
   type CompositionMetadata,
 } from "../shared.js";
 import type { RenderJob } from "../../renderOrchestrator.js";
 
-const BROWSER_MEDIA_EPSILON = 0.0001;
-
 export interface ProbeStageInput {
   projectDir: string;
   workDir: string;

packages/producer/src/services/renderOrchestrator.test.ts

@@ -6,7 +6,6 @@ import type { EngineConfig, ExtractedFrames } from "@hyperframes/engine";
 import type { CompiledComposition } from "./htmlCompiler.js";
 
 import {
-  applyRenderModeHints,
   buildMissingFrameRetryBatches,
   collectVideoMetadataHints,
   collectVideoReadinessSkipIds,
@@ -19,16 +18,19 @@ import {
   getNextRetryWorkerCount,
   isRecoverableParallelCaptureError,
   materializeExtractedFramesForCompiledDir,
-  projectBrowserEndToCompositionTimeline,
-  resolveDeviceScaleFactor,
   resolveRenderWorkerCount,
   resolveCompositeTransfer,
   selectCaptureCalibrationFrames,
   shouldFallbackToScreenshotAfterCalibrationError,
   shouldUseLayeredComposite,
   shouldUseStreamingEncode,
-  writeCompiledArtifacts,
 } from "./renderOrchestrator.js";
+import {
+  applyRenderModeHints,
+  projectBrowserEndToCompositionTimeline,
+  resolveDeviceScaleFactor,
+  writeCompiledArtifacts,
+} from "./render/shared.js";
 import { toExternalAssetKey } from "../utils/paths.js";
 
 describe("extractStandaloneEntryFromIndex", () => {

packages/producer/src/services/renderOrchestrator.ts

@@ -546,14 +546,6 @@ export class RenderCancelledError extends Error {
   }
 }
 
-export {
-  type CompositionMetadata,
-  applyRenderModeHints,
-  projectBrowserEndToCompositionTimeline,
-  resolveDeviceScaleFactor,
-  writeCompiledArtifacts,
-} from "./render/shared.js";
-
 function updateJobStatus(
   job: RenderJob,
   status: RenderStatus,