Feature: Support Default Duration Before Media Loads

[luwes]

timeFeature (packages/core/src/dom/store/features/time.ts) reports duration: 0 until the media fires loadedmetadata / durationchange. With preload="none", this means time displays show 0:00 until the user starts playback — even when the real duration is already known (e.g. from a CMS). Apps that defer loading for cost or bandwidth reasons can't show the correct length up front.

Add a configurable default duration that seeds the store's duration until the media reports its own, so the UI can render the known length without preloading. The real value should take over once metadata loads.

This depends on the same per-feature configuration mechanism being decided in #1728 (features are currently parameterless via definePlayerFeature).

Context

• Media Chrome defaultduration — uses the value as mediaduration before load, paired with preload="none"

[github-actions]

Planning Recommendations

Blocked by #1728 — this feature depends on the per-feature configuration mechanism being decided there (definePlayerFeature currently takes no params). Both issues share the same open question: factory like timeFeature({ defaultDuration }), store-level config slot, or attribute read at attach time. Resolving #1728 first unblocks implementation here.

Related issues to plan alongside:

• Feature: Make Controls Autohide Delay Configurable #1728 — Feature: Make Controls Autohide Delay Configurable — establishes the config shape this issue will consume
• Feature: Configurable Playback Rates #1404 — Feature: Configurable Playback Rates — same pattern of seeding feature state from app config

Milestone: GA (July 2026) — fits as a pre-GA quality-of-life feature; preload="none" + cost-conscious apps is a first-class use case at GA.

Priority recommendation: P2 — correctness gap for a real use case (deferred loading workflows), but not a playback blocker.

Epic: No obvious existing epic; may belong under a player configuration / feature parameterization epic once one is created.

Roadmap: Recommend adding once the per-feature config shape from #1728 is decided — the two issues should land together or in close sequence.