docs(prd): add git remote host override removal plan

docs/prds/0047-remove-git-remote-host-overrides.md

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+# PRD 0047: Remove Git Remote Host Overrides
+
+- **Status:** Draft
+- **Author:** didericis-codex
+- **Created:** 2026-06-02
+- **Issue:** #152
+
+## Summary
+
+Remove git remote host override plumbing from bottle manifests and git-gate
+startup. Git remote declarations should describe upstream repositories and the
+git-gate credential material needed to mirror them; they should not also
+configure hosts-file behavior for sidecars.
+
+## Problem
+
+The git remote model currently has a hosts override path that can make a git
+upstream resolve differently inside the git-gate sidecar. That is surprising
+because the same hostname may also be used for HTTP/API traffic that should keep
+using the normal egress DNS and policy path.
+
+Keeping host resolution in the git remote model makes repository routing,
+sidecar hosts files, and egress behavior feel coupled even when the operator
+only meant to configure git-gate.
+
+## Goals / Success Criteria
+
+- Git remote manifest parsing no longer stores host override data.
+- Git-gate upstream plans no longer carry host override data.
+- Docker compose rendering no longer emits sidecar `extra_hosts` entries from
+  git remote declarations.
+- Smolmachines bundle launch planning has no unused host override path for
+  git-gate.
+- Focused unit tests cover the absence of sidecar `extra_hosts` for git
+  upstreams.
+- Current user-facing documentation no longer advertises git remote host
+  overrides.
+
+## Non-goals
+
+- No replacement hosts-file override feature.
+- No SSH client config provisioning.
+- No change to git-gate's SSH credential or known-host handling.
+- No change to egress DNS, HTTP auth, or pipelock routing semantics.
+
+## Design
+
+Remove the host override field from the internal `GitEntry` and
+`GitGateUpstream` models. Remove the git-gate aggregation helper and the Docker
+compose code that converted those values into sidecar `extra_hosts`.
+
+The manifest parser does not need a migration-specific error path. After this
+change, the old hosts override key has no internal model field and no runtime
+effect.
+
+## Testing Strategy
+
+Run:
+
+- `python3 -m unittest discover -s tests/unit`
+
+## Open Questions
+
+None.