refactor: remove mini-swe-agent dependency — inline Docker/Modal backends (#2804)

Drop the mini-swe-agent git submodule. All terminal backends now use
hermes-agent's own environment implementations directly.

Docker backend:
- Inline the `docker run -d` container startup (was 15 lines in
  minisweagent's DockerEnvironment). Our wrapper already handled
  execute(), cleanup(), security hardening, volumes, and resource limits.

Modal backend:
- Import swe-rex's ModalDeployment directly instead of going through
  minisweagent's 90-line passthrough wrapper.
- Bake the _AsyncWorker pattern (from environments/patches.py) directly
  into ModalEnvironment for Atropos compatibility without monkey-patching.

Cleanup:
- Remove minisweagent_path.py (submodule path resolution helper)
- Remove submodule init/install from install.sh and setup-hermes.sh
- Remove mini-swe-agent from .gitmodules
- environments/patches.py is now a no-op (kept for backward compat)
- terminal_tool.py no longer does sys.path hacking for minisweagent
- mini_swe_runner.py guards imports (optional, for RL training only)
- Update all affected tests to mock the new direct subprocess calls
- Update README.md, CONTRIBUTING.md

No functionality change — all Docker, Modal, local, SSH, Singularity,
and Daytona backends behave identically. 6093 tests pass.

tests/test_minisweagent_path.py

@@ -1,34 +1,5 @@
-"""Tests for minisweagent_path.py."""
+"""Tests for minisweagent_path.py — REMOVED.
 
-from pathlib import Path
-
-from minisweagent_path import discover_minisweagent_src
-
-
-def test_discover_minisweagent_src_in_current_checkout(tmp_path):
-    repo = tmp_path / "repo"
-    src = repo / "mini-swe-agent" / "src"
-    src.mkdir(parents=True)
-
-    assert discover_minisweagent_src(repo) == src.resolve()
-
-
-def test_discover_minisweagent_src_falls_back_from_worktree_to_main_checkout(tmp_path):
-    main_repo = tmp_path / "main-repo"
-    (main_repo / ".git" / "worktrees" / "wt1").mkdir(parents=True)
-    main_src = main_repo / "mini-swe-agent" / "src"
-    main_src.mkdir(parents=True)
-
-    worktree = tmp_path / "worktree"
-    worktree.mkdir()
-    (worktree / ".git").write_text(f"gitdir: {main_repo / '.git' / 'worktrees' / 'wt1'}\n", encoding="utf-8")
-    (worktree / "mini-swe-agent").mkdir()  # empty placeholder, no src/
-
-    assert discover_minisweagent_src(worktree) == main_src.resolve()
-
-
-def test_discover_minisweagent_src_returns_none_when_missing(tmp_path):
-    repo = tmp_path / "repo"
-    repo.mkdir()
-
-    assert discover_minisweagent_src(repo) is None
+minisweagent_path.py was removed as part of dropping the mini-swe-agent
+dependency. These tests are no longer applicable.
+"""