docs(core): [SITE-04] document component lifecycle and selector contracts

refactor/changes/2026-09-16-SITE-04-components.md

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+# SITE-04 checkpoint: shared component contracts
+
+Six bilingual layers/controls/contextmenu guides now cover shared creation,
+configuration mutation, identity, insertion order, callbacks, updates and cleanup.
+The layer guide owns the common contract; the other guides link to it and explain
+their distinct return values, routing, selectors and desktop/mobile behavior.
+Existing runnable snippets are unchanged. Configuration tables now include
+beforeUnmount, numeric content/tooltips and the required top/left/right positions.
+
+The guides explain that update shallow-merges the original options before replacing
+the node, uses the merged beforeUnmount callback, and is not an atomic rollback.
+Controls retain undefined returns. Player destruction does not invoke every entry's
+beforeUnmount. The selector section covers initial labels, bound readonly metadata,
+HTML coercion, selection flags, latest-result ownership, removal and object reuse.
+Internal cache-entry types are not incorrectly advertised as runtime named exports.
+No production code, public declarations, dependencies or project scripts changed.
+
+The [core mapping](../core-content-review.json) adds 73 explicit declaration records
+from root/runtime component shapes and the three Artplayer manager properties.
+Total: 245 reviewed, 718 remaining out of 963. Counts include aliases and separate
+declaration shapes; they are not independent feature or overall completion counts.
+All seven previous groups' source and guide hashes were checked unchanged.
+
+## Verification
+
+- Six exact TS examples pass strict NodeNext with skipLibCheck:false and types:[].
+  All 24 previous Run Code snippets are unchanged and parse. Local links and
+  heading fragments resolve, including the shared component contract anchors.
+- Chromium 153.0.8010.12, Firefox 155.0 and Windows WebKit 26.6 pass 18 generated
+  page cases and all 72 code-forwarding checks. Popup targets are isolated; this
+  does not execute the online editor. Two Chromium screenshots were inspected.
+- Each engine passes 38 actual DOM assertions against core bytes matched to the
+  registered candidate. These cover manager aliases/cache/callbacks; duplicate,
+  missing, disabled and factory cases; ordering and numeric-zero fallbacks; shallow
+  replacement, listener release and throwing hooks; three control positions;
+  async selector races and removed results; item reuse/sharing; menu returns and
+  visibility; and destruction without per-entry hooks. No retries or page errors.
+- Existing component-resource/accessibility/documentation tests: 35 pass,
+  zero fail/skip, 1253.4366ms. This is not playback, SDK or physical-device proof.
+- Final build: 9.18s VitePress / 10.77s Yarn. LLM generation/check, inventory and
+  demo-route validation pass. Node 24.21.0, Yarn 1.22.22, TypeScript 5.9.3.
+- A failed edited-guide build is retained: bare generic type text was parsed as
+  HTML. Inline code formatting and accurate export wording fixed it. An earlier
+  ignored edit-helper fence syntax error happened before changing any guide.
+- All 21 library build envelopes remain valid; release blockers remain open.
+
+See [evidence](../baselines/site04-components.json). SITE-04 stays doing and totals
+remain 224/22/39. Continue remaining core groups, then the planned implementation
+checks. Formal review rounds remain user-directed. No push, deployment or publish.
+Revert this checkpoint to restore guides, generated pages, evidence and mapping.