Follow-ups from README refresh: publishing and stale-doc gaps

[mikemcdougall]

Follow-ups found while refreshing the README (PR #75). The README now documents the honest state; these are the underlying gaps:

• Publish the module to the Buf Schema Registry (buf.build/honua-io/geospatial-grpc per buf.yaml). CI publish step is skip-gated on an unconfigured BUF_TOKEN secret.
• Cut a stable (non-alpha) Geospatial.Grpc release — this is the gate blocking honua-sdk-dotnet's nuget.org publish (its publish workflow requires a stable feed).
• Repo's remote HEAD symref points at a nonexistent main branch (actual default is trunk) — check the GitHub default-branch setting.

[mikemcdougall]

Recon against current trunk (2026-07-27), item by item:

1. BSR publish — still open, operator-owned. The BSR module does not exist yet: buf.registry.module.v1.ModuleService/GetModules returns not_found for honua-io/geospatial-grpc. buf.yaml still names buf.build/honua-io/geospatial-grpc and the CI publish step remains skip-gated on the unconfigured BUF_TOKEN secret. Requires configuring the secret and pushing — registry/infra action, not a docs change.

2. Stable (non-alpha) Geospatial.Grpc release — still open, operator-owned. nuget.org search returns 0 hits for Geospatial.Grpc; the package ships to GitHub Packages only, and this remains the gate on honua-sdk-dotnet's nuget.org publish (honua-sdk-dotnet#271). Requires cutting a release — release action, not a docs change.

3. Remote HEAD symref pointing at nonexistent main — resolved. gh api repos/honua-io/geospatial-grpc reports default_branch: trunk, and git ls-remote --symref now shows ref: refs/heads/trunk HEAD. This box can be ticked.

No doc-side follow-up is needed: the README already documents the honest state (alpha, GitHub Packages only, no BSR-availability claim), and a sweep found no stale main-branch references in docs or workflows. Recommend ticking item 3 and keeping this issue open to track the two remaining operator actions (or splitting them out if preferred).