fix(player): handle Infinity duration; add lint rules for data-duration and Math.ceil overshoot (#243)

* fix(player): handle Infinity duration from runtime gracefully

When compositions have repeating animations without data-duration, the
runtime sends durationInFrames: Infinity. The player now ignores
non-finite duration values instead of displaying "Infinity:NaN" in the
controls. formatTime also returns "0:00" for non-finite inputs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat(lint): add data-duration and Math.ceil overshoot rules

- Add root_composition_missing_data_duration warning when the root
  composition element is missing data-duration, which causes the runtime
  to infer Infinity for loop-inflated timelines.
- Add gsap_repeat_ceil_overshoot warning that catches
  repeat: Math.ceil(d/c)-1 patterns which overshoot the intended
  duration. Recommends Math.floor instead.
- Fix gsap_infinite_repeat fixHint to suggest Math.floor (not Math.ceil).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(player): wait for injected runtime before declaring ready

When the player auto-injects the runtime script (because the
composition has GSAP timelines but no runtime), it would immediately
declare ready on the next probe cycle — before the runtime script
finished loading from CDN. This caused play() to send a postMessage
that nobody received, making autoplay silently fail.

Now the probe waits for the runtime bridge (__hf or __player) to
appear before proceeding to the ready state.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/core/src/lint/rules/composition.ts

@@ -210,6 +210,26 @@ export const compositionRules: Array<(ctx: LintContext) => HyperframeLintFinding
     return findings;
   },
 
+  // root_composition_missing_data_duration
+  ({ rootTag }) => {
+    const findings: HyperframeLintFinding[] = [];
+    if (!rootTag) return findings;
+    const compId = readAttr(rootTag.raw, "data-composition-id");
+    if (!compId) return findings;
+    const hasDuration = readAttr(rootTag.raw, "data-duration") !== null;
+    if (!hasDuration) {
+      findings.push({
+        code: "root_composition_missing_data_duration",
+        severity: "warning",
+        message: `Root composition "${compId}" is missing data-duration. Without an explicit duration, the runtime may infer Infinity for compositions with repeating animations, causing playback issues.`,
+        fixHint:
+          'Add data-duration="X" to the root composition element, where X is the total duration in seconds.',
+        snippet: truncateSnippet(rootTag.raw),
+      });
+    }
+    return findings;
+  },
+
   // standalone_composition_wrapped_in_template
   ({ rawSource, options }) => {
     const findings: HyperframeLintFinding[] = [];

packages/core/src/lint/rules/gsap.ts

@@ -500,9 +500,40 @@ export const gsapRules: Array<(ctx: LintContext) => HyperframeLintFinding[]> = [
           message:
             "GSAP tween uses `repeat: -1` (infinite). Infinite repeats break the deterministic " +
             "capture engine which seeks to exact frame times. Use a finite repeat count calculated " +
-            "from the composition duration: `repeat: Math.ceil(duration / cycleDuration) - 1`.",
+            "from the composition duration: `repeat: Math.floor(duration / cycleDuration) - 1`.",
           fixHint:
-            "Replace `repeat: -1` with a finite count, e.g. `repeat: Math.ceil(totalDuration / singleCycleDuration) - 1`.",
+            "Replace `repeat: -1` with a finite count, e.g. `repeat: Math.floor(totalDuration / singleCycleDuration) - 1`. " +
+            "Use Math.floor (not Math.ceil) to ensure the animation fits within the total duration.",
+          snippet: truncateSnippet(snippet),
+        });
+      }
+    }
+    return findings;
+  },
+
+  // gsap_repeat_ceil_overshoot
+  ({ scripts }) => {
+    const findings: HyperframeLintFinding[] = [];
+    for (const script of scripts) {
+      const content = script.content;
+      // Match patterns like: repeat: Math.ceil(duration / X) - 1
+      // or repeat: Math.ceil(totalDuration / cycleDuration) - 1
+      const pattern = /repeat\s*:\s*Math\.ceil\s*\([^)]+\)\s*-\s*1/g;
+      let match: RegExpExecArray | null;
+      while ((match = pattern.exec(content)) !== null) {
+        const contextStart = Math.max(0, match.index - 40);
+        const contextEnd = Math.min(content.length, match.index + match[0].length + 40);
+        const snippet = content.slice(contextStart, contextEnd).trim();
+        findings.push({
+          code: "gsap_repeat_ceil_overshoot",
+          severity: "warning",
+          message:
+            "GSAP repeat calculation uses `Math.ceil` which can overshoot the composition duration. " +
+            "For example, Math.ceil(10.5 / 2) - 1 = 5 repeats → 6 cycles × 2s = 12s, exceeding 10.5s.",
+          fixHint:
+            "Use `Math.floor` instead of `Math.ceil` to ensure the animation fits within the duration: " +
+            "`repeat: Math.floor(totalDuration / cycleDuration) - 1`. " +
+            "Math.floor(10.5 / 2) - 1 = 4 repeats → 5 cycles × 2s = 10s ✓",
           snippet: truncateSnippet(snippet),
         });
       }