test: make tests/ mirror the source tree; drop issue numbers from filenames

`scripts/run_tests.sh tests/<dir>/` is how a change gets its regression
coverage run, so a test filed under the wrong directory is a test nobody
runs when that code changes. Two kinds of drift had accumulated.

Parallel directories for one source package, folded into the mirror:
  tests/acp        -> tests/acp_adapter   (its __init__/conftest move with it)
  tests/cli        -> tests/hermes_cli    (prompt_toolkit fixture merged into
                                           hermes_cli/conftest.py)
  tests/run_agent  -> tests/agent         (backoff fixture becomes
                                           agent/conftest.py)
  tests/relay      -> tests/gateway/relay
  tests/state      -> tests/hermes_state

246 loose files at tests/ root, routed by the package they import/patch:
hermes_cli, hermes_state, agent, gateway, tools, plugins, tui_gateway, cron.
Installer and desktop-update script tests go to tests/scripts/{install,
desktop_update}/. 43 tests of root-level modules (batch_runner, utils,
hermes_constants, packaging) stay at the root.

Filenames drop their issue numbers (95 files: test_89315_x.py -> test_x.py);
the number stays in the module docstring where it has context.

Collisions: test_cli_skin_integration.py existed in both tests/ and tests/cli
with different subsets — merged into one (10 tests, all kept);
run_agent/test_pre_compress_memory_context.py -> agent/..._handoff.py;
tests/test_account_usage.py -> agent/test_account_usage_fetch.py;
tests/test_web_server.py -> hermes_cli/test_web_server_ws_ping.py.
Deleted: test_minisweagent_path.py (empty since PR #2804),
test_model_picker_scroll.py (tested a private copy of the logic, imported
nothing), test_process_loop_event_loop_warning.py (asserted asyncio behaviour,
imported nothing from Hermes).

Repo-root path arithmetic (Path(__file__).parents[N], dirname chains) is
bumped for the 202 files that changed depth and verified by evaluating every
such expression against the new location. classify_changes' desktop-updater
lane prefix, tests-os.yml's ignore glob and every in-tree path comment follow
the moves. tests/test_tests_tree_layout.py keeps the tree from drifting back.

tests/test_install_lockfile_churn.py

@@ -1,110 +0,0 @@
-"""Regression: installer update should discard pure npm lockfile churn.
-
-Desktop/bootstrap installs update an existing managed checkout in place. Local
-build steps often rewrite tracked ``package-lock.json`` without touching the
-matching ``package.json``; treating that churn as a real local edit forces an
-autostash and can abort the repository stage before the desktop comes back up.
-
-The installer should discard that generated churn before its stash/checkout
-logic, while still preserving intentional package edits where ``package.json``
-and ``package-lock.json`` changed together.
-"""
-
-from __future__ import annotations
-
-import re
-import shutil
-import subprocess
-from pathlib import Path
-
-import pytest
-
-REPO_ROOT = Path(__file__).resolve().parent.parent
-INSTALL_SH = REPO_ROOT / "scripts" / "install.sh"
-INSTALL_PS1 = REPO_ROOT / "scripts" / "install.ps1"
-
-pytestmark = pytest.mark.skipif(
-    shutil.which("git") is None or shutil.which("bash") is None,
-    reason="needs git and bash",
-)
-
-
-def _git(cwd: Path, *args: str, check: bool = True) -> subprocess.CompletedProcess:
-    return subprocess.run(
-        ["git", "-c", "user.email=t@t", "-c", "user.name=t", *args],
-        cwd=cwd,
-        check=check,
-        capture_output=True,
-        text=True,
-    )
-
-
-def _extract_install_sh_function(name: str) -> str:
-    text = INSTALL_SH.read_text()
-    match = re.search(rf"{name}\(\) \{{.*?\n\}}", text, re.DOTALL)
-    assert match is not None, f"{name}() not found in install.sh"
-    return match.group(0)
-
-
-def _extract_install_sh_autostash_block() -> str:
-    text = INSTALL_SH.read_text()
-    match = re.search(
-        r'local autostash_ref="".*?\n            fi\n',
-        text,
-        re.DOTALL,
-    )
-    assert match is not None, "autostash block not found in install.sh"
-    return match.group(0)
-
-
-@pytest.mark.live_system_guard_bypass
-def test_install_sh_discards_runtime_lockfile_churn_before_stash(
-    tmp_path: Path,
-) -> None:
-    repo = tmp_path / "hermes-agent"
-    repo.mkdir()
-    _git(repo, "init")
-    (repo / "package.json").write_text('{"dependencies":{"a":"1"}}\n')
-    (repo / "package-lock.json").write_text('{"lock":"old"}\n')
-    _git(repo, "add", "package.json", "package-lock.json")
-    _git(repo, "commit", "-m", "init")
-
-    (repo / "package-lock.json").write_text('{"lock":"runtime-churn"}\n')
-
-    script = (
-        "set -e\n"
-        'log_info() { echo "INFO: $*"; }\n'
-        'INSTALL_DIR="$PWD"\n'
-        f"{_extract_install_sh_function('discard_update_lockfile_churn')}\n"
-        "run() {\n"
-        f"{_extract_install_sh_autostash_block()}"
-        "}\n"
-        "run\n"
-    )
-    res = subprocess.run(
-        ["bash", "-c", script], cwd=repo, capture_output=True, text=True
-    )
-
-    assert res.returncode == 0, res.stderr
-    assert "Discarded npm lockfile churn (1 file(s))" in res.stdout
-    assert _git(repo, "stash", "list").stdout.strip() == ""
-    assert (repo / "package-lock.json").read_text() == '{"lock":"old"}\n'
-
-
-def test_install_sh_discards_lockfile_churn_before_status_probe() -> None:
-    text = INSTALL_SH.read_text()
-    idx_cleanup = text.index('discard_update_lockfile_churn "$INSTALL_DIR"')
-    idx_status = text.index('if [ -n "$(git status --porcelain)" ]')
-    idx_stash = text.index("git stash push --include-untracked")
-    assert idx_cleanup < idx_status < idx_stash
-
-
-def test_install_ps1_discards_lockfile_churn_before_status_probe() -> None:
-    text = INSTALL_PS1.read_text()
-    assert "function Discard-LockfileChurn" in text
-    idx_cleanup = text.index("Discard-LockfileChurn $InstallDir")
-    idx_status = text.index(
-        "$statusOut = git -c windows.appendAtomically=false status --porcelain"
-    )
-    idx_stash = text.index("stash push --include-untracked")
-    assert idx_cleanup < idx_status < idx_stash