fix: storyboard-angle review follow-ups (M1 bg-on-clip, B3 slideshow, parser guard, CLI fixes) (#1791)

* fix(skills): storyboard review — bg-on-clip rule, slideshow output, parser parity guard

Addresses the storyboard-angle review (jrusso1020):

- M1 (invisible text): frame-worker.md (x3) + SKILL.md Step 5 (x3) now require a
  frame's full-bleed background on a class=clip layer, never the #root /
  data-composition-id element (the root is clip-gated to its scene window, so a
  background on it is not a dependable ground and dark text can land on the black
  host body). The assembler already paints frame.md's canvas onto index #root as
  the base ground; the per-frame clip rides on top.
- B3 (slideshow truncates to slide 1): slideshow/SKILL.md gains an Output section
  (decks render via 'present'; 'render index.html' captures only the first
  composition; linear main-line MP4 export is deferred).
- Parser drift: vendoredParity.test.ts guards the three vendored storyboard.mjs
  copies (byte-identical + parse-parity with @hyperframes/core).
- skills-manifest.json regenerated for the edited SKILL.md files.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(cli): storyboard review — lint, validate help, snapshot, inspect, capture, render

Addresses the CLI findings from the storyboard-angle review (jrusso1020):

- lint (@hyperframes/lint): accept vendor-prefixed system-font keywords
  -apple-system / BlinkMacSystemFont so a system stack with a generic fallback no
  longer trips font_family_without_font_face (+ test).
- help: list 'validate' under Project in 'hyperframes --help' (was runnable but
  undocumented).
- snapshot: honor -o/--output (the flag did not exist; output was hardcoded to
  snapshots/). The dir is resolved once and threaded through capture + contact
  sheet + Gemini.
- snapshot: split font status into loaded / error / unused with a one-line
  summary; only a real 'error' is reported as FAILED (an unrequested @font-face
  is 'unused', not a contradiction with 'loaded').
- inspect: suppress text_occluded across a scene-to-scene crossfade (occluder in
  a different data-composition-id mount while a scene is mid-fade); a same-scene
  or two-settled-scenes overlap still flags.
- inspect: suppress content_overlap between in-flow siblings governed by the same
  flex/grid container (tight stacks / number lockups are layout slop).
- capture: record source resolution (videoWidth/Height) in video-manifest.json
  alongside the DOM display box; consumers size off the source dims.
- render: warn when the target carries a slideshow island (render captures only
  the first scene, so the MP4 is truncated to slide 1; use 'present').

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/lint/src/rules/fonts.test.ts

@@ -261,6 +261,16 @@ describe("font rules", () => {
       expect(findings).toHaveLength(0);
     });
 
+    it("does not flag vendor-prefixed system-font keywords (-apple-system, BlinkMacSystemFont)", async () => {
+      const html = `<div data-composition-id="test" data-width="1920" data-height="1080">
+        <style>
+          body { font-family: -apple-system, BlinkMacSystemFont, system-ui, sans-serif; }
+        </style>
+      </div>`;
+      const findings = await findByCode(html, "font_family_without_font_face");
+      expect(findings).toHaveLength(0);
+    });
+
     it("does not flag installed registry blocks that declare fonts via Google Fonts", async () => {
       const html =
         `<!-- hyperframes-registry-item: my-block -->\n` +

packages/lint/src/rules/fonts.ts

@@ -16,6 +16,12 @@ const GENERIC_FAMILIES = new Set([
   "math",
   "emoji",
   "fangsong",
+  // Vendor-prefixed system-font keywords. Like `system-ui`, the engine resolves
+  // these to the OS UI font — they are never installable files and must not be
+  // flagged as a missing @font-face, even when a generic fallback follows them
+  // (e.g. `-apple-system, system-ui, sans-serif`).
+  "-apple-system",
+  "blinkmacsystemfont",
   "inherit",
   "initial",
   "unset",