feat(cli): accept ffmpeg-style rational fps (NTSC, PAL, slow-mo)

Replaces the rigid `--fps 24|30|60` whitelist with a numeric range and
adds support for ffmpeg-style fractional framerates so NTSC stays exact
end-to-end.

- `--fps 30` keeps working (integer fps)
- `--fps 30000/1001` now means exact NTSC 29.97 (not the lossy decimal)
- `--fps 24000/1001`, `--fps 60000/1001`, `--fps 25/50/120/240` all work
- Decimals like `--fps 29.97` are rejected with a friendly error pointing
  the user at the rational form, since `29.97` and `30000/1001` round
  to different framerates inside ffmpeg

Carries an `Fps = { num: number; den: number }` rational end-to-end:
RenderConfig, EncoderOptions, StreamingEncoderOptions, CaptureOptions,
DockerRenderOptions, Studio API request body, regression-harness
meta.json. The `-r` and `-framerate` ffmpeg args emit the rational form
verbatim (`30000/1001`) so no decimal round-trip happens at the encoder
boundary. Frame-interval math uses `1000 * den / num` ms (33.366… for
NTSC, 33.333… for integer 30).

Helpers live in @hyperframes/core:
- `parseFps(input: string | number): FpsParseResult` — discriminated
  parser used by both the CLI and the Studio API route
- `fpsToFfmpegArg(fps: Fps): string` — emits "30" or "30000/1001"
- `fpsToNumber(fps: Fps): number` — for arithmetic (telemetry, frame
  count, frame-index → time)

Studio API wire format accepts polymorphic `fps: number | string`:
- number → integer fps (`30`)
- string → rational (`"30000/1001"`)
Decimals are rejected; matches the same rule as the CLI.

Existing meta.json fixtures with integer `"fps": 30` continue to load
unchanged — the regression-harness validator now normalizes both number
and string inputs through `parseFps`.

packages/cli/src/utils/dockerRunArgs.ts

@@ -7,6 +7,8 @@
  * a test in `dockerRunArgs.test.ts` — that combination is what catches
  * silent-drop regressions like the one that lost `--hdr` historically.
  */
+import { fpsToFfmpegArg, type Fps } from "@hyperframes/core";
+
 export interface DockerRunArgsInput {
   imageTag: string;
   /** Absolute host path to the project directory (mounted read-only at /project). */
@@ -19,7 +21,13 @@ export interface DockerRunArgsInput {
 }
 
 export interface DockerRenderOptions {
-  fps: 24 | 30 | 60;
+  /**
+   * Frame rate as an exact rational; see `Fps` in @hyperframes/core. The
+   * docker-run arg builder serializes this back to a `--fps` string
+   * (`"30"` or `"30000/1001"`) which the in-container CLI re-parses with
+   * `parseFps`, so the rational survives the host → container hop.
+   */
+  fps: Fps;
   quality: "draft" | "standard" | "high";
   format: "mp4" | "webm" | "mov" | "png-sequence";
   workers?: number;
@@ -54,7 +62,7 @@ export function buildDockerRunArgs(input: DockerRunArgsInput): string[] {
     "--output",
     `/output/${outputFilename}`,
     "--fps",
-    String(options.fps),
+    fpsToFfmpegArg(options.fps),
     "--quality",
     options.quality,
     "--format",