Replace the hardcoded FORGE_HTTP const with forge_http_base() which
reads HIVE_FORGE_URL from the environment (already set unconditionally
by hive-c0re.nix to http://<forge.domain>). Add forge_git_url() helper
that inserts core:<token> credentials between scheme and authority for
git push/clone URLs.
All call sites updated:
- forge/mod.rs: api() OnceLock + new forge_git_url/forge_http_base fns
- forge/repos.rs: push_meta, push_config, ensure_meta_remote
- forge/pr_merge.rs: tokenised_repo_url delegate + test loosened
- workers/knowledge.rs: clone + push URLs
- socket_server/mod.rs: clone_url in RepoCreated response
No new env var: HIVE_FORGE_URL was already the right knob (mara).
Closes#1868. Closes#2174 (this supersedes the operators-team fix from
the closed#2218, which is re-applied in the ensure_operators_team call
that was already merged separately).
