Versioning: local builds as 0.0.0 and allow x.y.0 as the first release of a prefix

[jernejk]

Today local builds are <VersionPrefix>.0 (0.3.0) and the release workflow computes the next patch from existing tags, so the first release on a new prefix is x.y.1 and release-notes/AGENTS.md reserves patch-zero for developer builds. That made this release 0.3.1 when 0.3.0 was intended.

Proposal:

• Local builds use 0.0.0-local (or 0.0.0) so a dev build can never be confused with a published one and tp --version makes it obvious.
• The workflow starts at .0 when no tag exists for the prefix, and .N+1 otherwise.
• release-notes/AGENTS.md, docs/Instructions-Deployment.md and the csproj comment updated to match, and ReleaseNotesCatalogTests checked for assumptions.

Do this before the 0.4 release so it can be 0.4.0.