feat(telemetry): attribute renders to the authoring workflow skill (#1695)

* feat(telemetry): attribute renders to the authoring workflow skill

Add an optional `--skill` flag to `hyperframes render` and tag the
`render_complete` / `render_error` events with `authoring_skill`, so render
usage can be broken down per authoring workflow. The value is slug-gated (a
malformed value is ignored) and the existing anonymous / opt-out telemetry
pipeline is otherwise unchanged.

Each end-user workflow that renders now passes `--skill=<name>` on its render
command: embedded-captions, faceless-explainer, graphic-overlays,
motion-graphics, music-to-video, pr-to-video, product-launch-video,
remotion-to-hyperframes, website-to-video.

Not instrumented, by design: general-video renders freeform with no canonical
render command to attach to, and slideshow produces an interactive deck rather
than a rendered video. Both can follow up if per-skill numbers are wanted.

* fix(telemetry): address review — shared slug util, equals-form flag, invalid-value warning

- Extract the SKILL_SLUG regex + a normalizeSkillSlug() helper into
  telemetry/skill.ts, shared by the `events` and `render` commands (the regex
  was duplicated). `render` adopts normalizeSkillSlug (so it now trims the value,
  matching `events`); `events` references the shared SKILL_SLUG. + unit test.
- `render` warns on a non-empty but invalid --skill value (e.g. a camelCase
  typo) so attribution isn't silently lost — stderr only, never fails the render.
- embedded-captions render script: `--skill embedded-captions` -> `--skill=embedded-captions`.
  On an older CLI that does not declare --skill, the space form leaks the value
  as a positional and clobbers the project dir (resolveProject fails); the equals
  form is parsed as a self-delimiting flag and safely ignored. Verified via Node
  parseArgs(strict:false).

Addresses review feedback on the PR (shared util + .trim drift, version-skew
safety, invalid-value visibility).

---------

Co-authored-by: kiritowoo <295860553+kiritowoo@users.noreply.github.com>

skills/remotion-to-hyperframes/SKILL.md

@@ -86,7 +86,7 @@ Run the eval harness — [`references/eval.md`](references/eval.md) for the full
 cd remotion-src && npx remotion render <CompositionId> out/baseline.mp4
 
 # Render HF translation
-cd ../hf-src && npx hyperframes render --output ../hf.mp4
+cd ../hf-src && npx hyperframes render --skill=remotion-to-hyperframes --output ../hf.mp4
 
 # SSIM diff
 ../../scripts/render_diff.sh ./remotion-src/out/baseline.mp4 ./hf.mp4 ./diff