Default installer and upgrade fail on retired compatibility-evidence URL

[rmcdaniel]

The default CLI installer and upgrade flow still request https://durable-workflow.com/public-artifact-compatibility-evidence.json. That endpoint was removed when the 2.0 docs were simplified; it currently returns HTTP 404. As a result, default installs and upgrades fail, including the post-publication verification in CLI 2.1.1 release run 36026197333. The 2.1.1 release assets themselves are published and the PHAR checksum/version/help were verified independently.

Fix the CLI's default channel discovery using a current, public release authority without resurrecting the retired aggregate evidence pipeline. Preserve explicit version pinning and checksum verification. Qualify the installer/upgrade path using the published artifact, then release a patch. Do not alter cancellation or runtime semantics.

[rmcdaniel]

Scope correction from a live check: https://durable-workflow.com/install.sh already defaults to GitHub latest/stable and works. The broken paths are the installer scripts bundled in CLI 2.1.1 release assets and unpinned dw upgrade. PR #34 removes their dependency on the retired endpoint. The source installer was verified against the published 2.1.1 asset; the 2.1.2 release is in progress.

[rmcdaniel]

Fixed by merged PR #34 and published CLI 2.1.2 (tag/source 3c4bc7a). The public stable-release manifest now advertises 2.1.2 (docs PR #140); release reconciliation run 36031960053 passed. Independent published-artifact checks: all downloaded asset checksums matched SHA256SUMS; the bundled install.sh installed 2.1.2 from GitHub latest; the published standalone binary reported 2.1.2 and unpinned dw upgrade --dry-run resolved 2.1.2; the release-channel check returned stable/2.1.2. The top-level site installer was already healthy, as noted above. No retired compatibility-evidence endpoint was restored.