ci: publish tested plugin releases automatically

[zemrip-server]

What changed

A successful merge previously produced no GitHub Release. After the complete push CI succeeds for the current bluff commit, the new workflow creates an unsigned version tag and Release, then directly notifies nvim-config with that exact commit. The first version is v0.1.0; subsequent automatic releases increment the patch above the highest stable version.

Superseded or unsuccessful CI cannot publish. Reruns reuse an existing tag/release, interrupted publication resumes, and tag collisions or API failures stop without moving tags. Missing dispatch configuration fails visibly after publication. The old release/manual notification remains for recovery; the direct post-CI notification is replaced by publication followed by notification.

Scope

• Automation and release documentation; no plugin UI/runtime changes.
• Human-approved unsigned CI tags for this Lua plugin. Agent Manager retains its separate signed-release policy.
• The existing NVIM_CONFIG_DISPATCH_TOKEN enables downstream adoption; no new signing credential is required.

Validation

• Release fixtures cover initial publication, patch numbering, reruns, partial publication, stale CI, API failure, tag collision, and draft collision.
• Actionlint, ShellCheck, Lua compilation, documented plugin tests/integration checks, help tags, and whitespace checks passed locally.
• No mise verify task is declared in this repository. Tests used local synthetic fixtures and no live release was published during verification.
• Target: bluff. Brokered automation commit is intentionally unsigned.

The workflow activates after merge. nvim-config PR #49 adds automatic merging of tested dependency updates on separate per-plugin branches.