chore(release): promote v0.2.0 manifest

[Jowitt13]

Promote the published v0.2.0 release

Changes

• promotes the root install manifest and SHA256SUMS.txt to the already-published v0.2.0 assets;
• sets the root engine and published-release constants to 0.2.0;
• advances the next unpublished candidate to v0.2.1, preserving the distinct-tag invariant;
• synchronizes current installation documentation and records the complete promotion procedure in the release checklist.

Evidence

• pnpm run verify:cloud — passed (685 tests / 34 files);
• pnpm run verify:published-release -- --tag v0.2.0 — downloaded release assets, integrity and LF reproducibility passed;
• root SHA256SUMS.txt has the same SHA-256 as the published checksum asset.

No algorithm, dependency, Release asset, tag, or manifest promotion beyond the already-published v0.2.0 assets is included.