chore(infra): add gRPC layer, update protobufs, remove immediate module

- Add gRPC service modules: auth, channel, channel settings, member,
  permission
- Update protobuf definitions and generated code
- Remove immediate/ real-time module (superseded by IM service)
- Update etcd discovery and registration
- Update cache, error, config, and build infrastructure
- Add ADR documentation
- Update OpenAPI spec

proto/git/commit.proto

@@ -154,6 +154,102 @@ message CompareCommitsResponse {
   Oid merge_base = 4;
 }
 
+
+message FindCommitRequest {
+  RepositoryHeader repository = 1;
+  ObjectSelector revision = 2;
+  bool include_stats = 3;
+}
+
+message ListCommitsByOidRequest {
+  RepositoryHeader repository = 1;
+  repeated bytes oids = 2; // binary OID values
+  bool include_stats = 3;
+}
+
+message ListCommitsByOidResponse {
+  repeated Commit commits = 1;
+}
+
+message CommitIsAncestorRequest {
+  RepositoryHeader repository = 1;
+  string ancestor_oid = 2;
+  string descendant_oid = 3;
+}
+
+message CommitIsAncestorResponse {
+  bool is_ancestor = 1;
+}
+
+message CheckObjectsExistRequest {
+  RepositoryHeader repository = 1;
+  repeated string revisions = 2; // hex OIDs or rev expressions
+}
+
+message RevisionExistence {
+  string revision = 1;
+  bool exists = 2;
+}
+
+message CheckObjectsExistResponse {
+  repeated RevisionExistence revisions = 1;
+}
+
+message CommitsByMessageRequest {
+  RepositoryHeader repository = 1;
+  string query = 2;          // regex or literal to search in commit messages
+  string revision = 3;        // limit to this branch/ref (empty = all branches)
+  uint32 limit = 4;
+  uint32 offset = 5;
+  bool case_insensitive = 6;
+}
+
+message CommitsByMessageResponse {
+  repeated Commit commits = 1;
+}
+
+
+message GetCommitStatsRequest {
+  RepositoryHeader repository = 1;
+  ObjectSelector revision = 2;
+}
+
+message LastCommitForPathRequest {
+  RepositoryHeader repository = 1;
+  string path = 2;
+  string revision = 3; // limit history to this ref
+  bool literal_pathspec = 4;
+}
+
+message LastCommitForPathResponse {
+  Commit commit = 1;
+  string path = 2;
+}
+
+
+message CountCommitsRequest {
+  RepositoryHeader repository = 1;
+  string revision = 2;
+  string path = 3;
+  string since = 4; // ISO 8601 date
+  string until = 5;
+}
+
+message CountCommitsResponse {
+  uint64 count = 1;
+}
+
+message CountDivergingCommitsRequest {
+  RepositoryHeader repository = 1;
+  string left = 2;
+  string right = 3;
+}
+
+message CountDivergingCommitsResponse {
+  uint64 left_count = 1;
+  uint64 right_count = 2;
+}
+
 service CommitService {
   rpc ListCommits(ListCommitsRequest) returns (ListCommitsResponse);
   rpc GetCommit(GetCommitRequest) returns (Commit);
@@ -162,4 +258,15 @@ service CommitService {
   rpc RevertCommit(RevertCommitRequest) returns (CreateCommitResponse);
   rpc CherryPickCommit(CherryPickCommitRequest) returns (CreateCommitResponse);
   rpc CompareCommits(CompareCommitsRequest) returns (CompareCommitsResponse);
+
+  rpc FindCommit(FindCommitRequest) returns (Commit);
+  rpc ListCommitsByOid(ListCommitsByOidRequest) returns (ListCommitsByOidResponse);
+  rpc CommitIsAncestor(CommitIsAncestorRequest) returns (CommitIsAncestorResponse);
+  rpc CheckObjectsExist(CheckObjectsExistRequest) returns (CheckObjectsExistResponse);
+  rpc CommitsByMessage(CommitsByMessageRequest) returns (CommitsByMessageResponse);
+  rpc GetCommitStats(GetCommitStatsRequest) returns (CommitStats);
+  rpc LastCommitForPath(LastCommitForPathRequest) returns (LastCommitForPathResponse);
+
+  rpc CountCommits(CountCommitsRequest) returns (CountCommitsResponse);
+  rpc CountDivergingCommits(CountDivergingCommitsRequest) returns (CountDivergingCommitsResponse);
 }