feat!: migrate adapter to Molecule API

[aose-yuu]

Purpose

Migrate the React adapter from the legacy logic API to the molecule API in @sigrea/core.

Summary

• Renamed useLogic to useMolcule and replaced mountLogic/cleanupLogic with direct molecule creation and disposeMolecule.
• Kept React Strict Mode behavior by preserving the internal subscriber + pending-dispose tracking.
• Updated exports, docs, playground, tests (including strict-mode coverage), and changelog.
• Bumped @sigrea/core to ^0.4.0.

Breaking change / Migration

• useLogic(...) -> useMolcule(...)

Verification

• pnpm test (CI)
• pnpm typecheck (CI)
• pnpm build (CI)
• pnpm format (CI)
• CI PR title check passes (Conventional Commits)

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Restore @sigrea/core resolution in lockfile

The lockfile still lists @sigrea/core as a devDependency (lines 9-16) but its resolution block was removed (rg "@sigrea/core@" pnpm-lock.yaml now returns no matches), so pnpm install --frozen-lockfile will fail because the lock cannot resolve that package and will force a re-resolution. Reintroduce the package entry so installs remain reproducible.

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