chore(templates): seed the organization release-convention starter surface

[szmyty]

Outcome

Make the approved convention easy to adopt in new repositories without copying a full publishing workflow or accidentally granting write authority.

Scope

• Add opt-in repository templates/snippets for CHANGELOG.md, an Aether release declaration, AGENTS guidance, and Taskfile release handoff targets.
• Add safe pull-request validation and manual-dispatch release workflow entry points that pin the approved Relay revision.
• Document how a maintainer selects a profile and replaces placeholders before enabling publication.
• Keep registry credentials, package publication, container pushes, Pages deployment, and DOI integration out of the generic template.

Acceptance criteria

• A newly created repository can choose a profile and pass a local dry run without external credentials.
• Templates link to the canonical Aether/Hygiene documents rather than embedding forks.
• Write permissions are absent from pull-request paths and scoped only to explicit publish jobs.
• The template includes a migration note for existing repositories.

Dependencies

• spec(releases): define the organization-wide semantic release and changelog contract aether#61
• policy(releases): add the repository release-convention baseline profile hygiene#27
• feat(releases): publish reusable semantic-release preparation and verification workflows relay#47
• feat(releases): validate semantic release, changelog, and version-source conformance egolint#29