fix(renderer): preserve hydrated Show range ownership

[smiggleworth]

Summary

This resolves askr#164: hydration must preserve existing tail identity when an inactive <Show> precedes an active <Show> in the same boundary chain.

The branch adds a targeted SSR+SPA hydration fix and regression coverage for mixed populated Show tails.

Closes #164

[Copilot]

Pull request overview

This PR addresses askr#164 by tightening hydration cursor/ownership handling when empty <Show> boundaries precede populated boundaries/components, preventing tail duplication and preserving server-rendered node identity. It also extends SSR/SSG portal output with stable comment anchors to support strict hydration parity without inserting visible wrapper elements.

Changes:

• Preserve hydration cursor/ownership across empty Show boundaries and transparent multi-node component results (fragment/array), including rollback-safe range adoption.
• Introduce SSR portal anchor markers (askr-portal-anchor:*) and retain empty automatic portal host markers when needed for hydration stability.
• Add regression coverage for empty-Show tails, keyed For adoption after static siblings, component-returned arrays, and default portal hydration parity; update docs and version.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/jsdom/ssr/portal-rendering.test.tsx	Updates SSR expectations to include portal hydration anchors.
tests/jsdom/ssr/for-static-sibling-hydration.test.tsx	Adds regression test for keyed For adoption after a static sibling during hydration.
tests/jsdom/ssr/empty-show-tail-hydration.test.tsx	Adds regression coverage for empty Show boundaries preserving tail identity and rollback behavior.
tests/jsdom/ssr/default-portal-hydration-parity.test.tsx	Adds parity test ensuring default portal anchors/DOM topology remain stable through hydration and updates.
tests/jsdom/ssr/component-array-hydration.test.tsx	Adds hydration tests for component-returned arrays, nested scopes, and portal identity preservation.
tests/jsdom/ssg/static-gen.test.tsx	Updates SSG expectations to include retained portal anchor markers.
tests/jsdom/dom/component-array-structure.test.tsx	Adds SPA structure/update/rollback coverage for component-returned arrays.
src/ssr/render-sync.ts	Renders SSR_PORTAL_ANCHOR tokens and retains empty automatic host markers when required for hydration.
src/runtime/portal.ts	Emits SSR portal anchor tokens at writer sites; centralizes portal token creation.
src/runtime/context.ts	Makes scope providers transparent and introduces durable internal identity keys for hydration ownership.
src/runtime/component-commit.ts	Allows placeholder replacement to target comment hosts for ownership/placeholder tracking.
src/renderer/element-children.ts	Improves mixed control cursor handling and hydrator sync for components (incl. hydration range end + empty cursor preservation).
src/renderer/dom-host.ts	Extends syncComponentElement signature to support hydration range end and cursor preservation options.
src/renderer/component-range-commit.ts	Adds fast-path for transparent nested results during component range replacement.
src/renderer/component-host.ts	Supports SSR portal anchor comment hosts and adopts hydrated multi-node component ranges with bounded end cursors.
src/renderer/component-host-results.ts	Adds utilities for retaining owner chains and materializing empty hydration placeholders/SSR portal anchor adoption.
src/renderer/component-host-instances.ts	Extends identity matching to include internal identity keys and range-based matching for stable hydration.
src/renderer/component-fragment-range.ts	Implements adoption of hydrated multi-node ranges and preserves foreign automatic portal hosts during staging.
src/renderer/child-shape.ts	Defines “transparent component result” and “transparent range result” helpers used across hydration/commit paths.
src/renderer/boundary-range-sync.ts	Improves adoption gating for hydrated boundary elements and handles pending hydration in mixed parents.
src/renderer/boundary-range-adoption.ts	Adds canAdoptHydratedElement helper and extends host sync signature to match hydration needs.
src/renderer/boundaries.ts	Extends boundary host sync signature for hydration cursor/range handling.
src/common/portal.ts	Introduces portal anchor symbol, token helpers, and marker detection for hydration anchors.
src/common/control.ts	Adds transparent-result marking/detection for component result handling.
package.json	Bumps version to 0.0.78.
package-lock.json	Locks version bump to 0.0.78.
docs/guides/platform-recipes.md	Updates documented verified version to 0.0.78.
docs/core/rendering.md	Documents transparent component ranges and portal anchor retention behavior in SSR/SSG/hydration.

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