docs(site): [SITE-04] cross-check existing plugin guide semantics

refactor/changes/2026-09-16-SITE-04-existing-guides.md

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+# SITE-04 checkpoint: current semantics of five earlier plugin guides
+
+Cross-check the Chinese and English Danmuku, HLS Control, DASH Control, Audio
+Track and VTT Thumbnail guides against current source and public declarations.
+The ten guides retain all26 existing runnable snippets. Eight non-Danmuku
+snippets additionally match their original demo files exactly. No runtime,
+declaration, package README or dependency changed. DASH's packaged ARCHITECTURE
+clarifies the same synchronous-getter rule; its candidate requires a REL-02 refresh.
+
+Corrections and additions:
+
+- Restore visible Run Code text on both HLS and DASH language pages. Explain
+  synchronous SDK getters/formatters within asynchronously scheduled DASH refresh,
+  rather than implying Promise-returning SDK getters are supported. Record the
+  optional ordinary factory call and required final overload used by Parameters.
+- Correct Danmuku's English whitespace claim: direct and loaded comments preserve
+  text; the input panel trims it. Explain input defaulting mutations, shallow
+  queue copies, non-deduplicating ids, truthy filters, Owner versus registered
+  result, pooled nodes, unused slider show and exported icons versus bundled UI.
+- State VTT's exact progress endpoints and existing control/CSS hooks. Preserve
+  Audio Track's open Windows WebKit native buffering boundary independently of
+  passing source-switch order tests. Correct the English Proxies sidebar title.
+
+The [semantic tracker](../site-content-review.md) now includes these five packages.
+This leaves the core963 enumerated members for explicit semantic mapping. It does
+not substitute guide checks for SDK, media, physical-device or final-demo evidence.
+
+## Verification
+
+All10 exact TypeScript snippets pass strict NodeNext with skipLibCheck:false and
+types:[]. Each page's43–58 distinct local link/file/fragment targets resolve.
+All30 page cases pass on Chromium153.0.8010.12, Firefox155.0 and Windows WebKit26.6,
+with78 successful Run Code forwarding checks, no page errors and no retries within
+the final run. Screenshots are retained; Chromium Chinese HLS layout was inspected.
+Popup editor responses are isolated, so this is navigation rather than playback.
+
+Detailed results, source hashes, browser versions and retained failures are in
+[the evidence record](../baselines/site04-existing-guides.json). Node24.21.0,
+Yarn1.22.22 and TypeScript5.9.3 were used. Inventory remains66 Markdown,75 HTML,
+30 examples and204 assets; no new routes or task status transitions were added.
+
+The first documentation test run detected stale generated LLM content because it
+preceded build:llm. Regeneration followed by all17 tests passed in1209.7607ms.
+Two guide probe attempts failed on their translation-link selectors: first an
+absolute-href assumption, then a Danmuku-specific English-guide label. The final
+probe resolves actual relative URLs and handles both existing labels. These are
+recorded test-script failures, not player defects or silently retried assertions.
+
+build:docs passed in8.96s (Yarn10.51s), as did build:llm/check:llm, configuration
+lint, strict toolchain validation, inventory and historical demo path checks.
+The20 unaffected library build envelopes remain valid; DASH's prior candidate is
+stale after the packaged maintenance correction. All packages retain separate
+release blockers. Generated output came from repository scripts only.
+
+SITE-04 remains doing. Formal REVIEW-01/02/03 waits for user direction. No push,
+remote workflow dispatch, deployment or publication occurred. Reverting this
+checkpoint restores prior guide prose/navigation and generated assets.
+
+The complete staged whitespace check passes without generated-file exclusions.