[gohabereg]

Why

There is no way to tear an editor down. Neither Core nor EditorJS has a destroy(), so unmounting an editor (route change, component unmount, several editors on one page, React StrictMode) leaks the editor DOM, the document-wide selectionchange listener, the collaboration WebSocket, timers, and every tool and plugin instance. Several plugins already implement destroy(), and the core/sdk specs already say it's called on teardown, but nothing calls it.

Board card: Clean up (Core APIs).

What Changes

This PR is the OpenSpec change only (openspec/changes/editor-destroy). Implementation follows in stacked PRs.

• Core#destroy() / EditorJS#destroy(): synchronous, idempotent. Tears down plugins in reverse construction order (unregistering their public APIs), then UndoRedoManager, SelectionManager, BlockRenderer (each block's tool instance and adapter), the adapter plugin, and last ToolsManager. A throwing step is logged and teardown continues. The model is never mutated, so nothing reaches undo history or collaboration. use()/initialize() throw afterwards.
• Interrupted initialization: destroy() during a pending initialize() makes it reject with a DOMException named AbortError (the platform convention, as with fetch). Tool preparation stops too: ToolsManager aborts its own controller, so tools still queued aren't prepared and a tool whose prepare() settles afterwards is neither created nor announced. The bundle handles its own ready promise: AbortError is ignored, other init errors are logged, so neither is reported as an unhandled rejection; awaiting isReady still rejects.
• Tools: optional destroy() on BlockTool/InlineTool, called once per instance the editor creates:
  • Block tools: BlockRenderer owns each per-block instance.
  • Inline tools: InlineToolFacade.create() returns one instance per tool, shared by formatting, selection and the inline toolbar. None of those consumers destroys it. The facade does, once, through ToolsManager, as the last step of teardown (D7).
• Adapter plugin: destroy() becomes required on EditorJSAdapterPlugin.
• Repo-wide listener rule (architecture spec): every component releases listeners through one AbortController; unsubscribe functions returned by onUpdate/onCaretUpdate are tied to its abort event. SDK base classes (BlockToolAdapter) own the controller and expose a protected signal to subclasses.
• Shared selectionchange watcher: reference-counted, so several editors can be destroyed independently.
• UI: teardown for every UI plugin is covered by fix(ui): remove blocks holder listeners and detach it on destroy #174, so this change has no UI plugin implementation. InlineToolbarUI doesn't destroy inline tool instances either, because they're shared (D7).

Modified capabilities: architecture, core, sdk, dom-adapters, editorjs-bundle. Supersedes the "Core currently does not expose a global destroy()" note in docs/plugins.md (docs are updated in the implementation PR).

Stack

1. This PR: spec
2. feat(core): add editor destroy lifecycle #196 — lifecycle and API changes: Core/EditorJS destroy(), core services, tool contracts, BlockToolAdapter controller (targets this branch)
3. feat: implement destroy() in adapters and plugins #207 — adapters, plugins, e2e tests and the archive (stacked on feat(core): add editor destroy lifecycle #196)

Verification

• openspec validate editor-destroy --type change passes.
• tasks.md is intentionally unchecked here; implementation PRs check off their tasks.

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