fix(cli): align session list table for CJK terminal width

Replace str.ljust-based columns with east_asian_width-aware padding so
`hermes sessions list` and inline /history session picks line up when
titles/previews mix Chinese and ASCII. Share one formatter via
print_sessions_table in hermes_cli/main.py.

test(cli): add coverage for display-width helpers in
tests/hermes_cli/test_session_display_width.py.

tests/hermes_cli/test_session_display_width.py

@@ -0,0 +1,133 @@
+"""Tests for CJK-aware session list column padding (hermes_cli.main display helpers)."""
+
+from unittest.mock import patch
+
+from hermes_cli.main import (
+    _fit_display_width,
+    _pad_display_right,
+    _text_display_width,
+    print_sessions_table,
+)
+
+
+class TestTextDisplayWidth:
+    def test_empty(self) -> None:
+        assert _text_display_width("") == 0
+
+    def test_ascii(self) -> None:
+        assert _text_display_width("abc") == 3
+
+    def test_wide_cjk(self) -> None:
+        # Typical Han characters are wide (W) — two terminal cells each.
+        assert _text_display_width("中文") == 4
+
+    def test_mixed(self) -> None:
+        assert _text_display_width("a中") == 1 + 2
+
+
+class TestFitDisplayWidth:
+    def test_no_truncation_when_fits(self) -> None:
+        assert _fit_display_width("hello", 10) == "hello"
+
+    def test_truncates_with_ellipsis(self) -> None:
+        out = _fit_display_width("abcdefghij", 5)
+        assert out.endswith("…")
+        assert _text_display_width(out) <= 5
+
+    def test_cjk_truncation_respects_cells(self) -> None:
+        s = "一二三四五六"
+        out = _fit_display_width(s, 5)
+        assert out.endswith("…")
+        assert _text_display_width(out) <= 5
+
+    def test_max_cells_zero_returns_empty(self) -> None:
+        assert _fit_display_width("hello", 0) == ""
+
+
+class TestPadDisplayRight:
+    def test_pads_ascii_to_width(self) -> None:
+        assert _pad_display_right("hi", 8) == "hi      "
+        assert _text_display_width(_pad_display_right("hi", 8)) == 8
+
+    def test_pads_mixed_to_display_width(self) -> None:
+        # "a" + two wide chars = 1 + 4 = 5 cells; pad to 8 → 3 spaces
+        got = _pad_display_right("a中文", 8)
+        assert _text_display_width(got) == 8
+        assert got.startswith("a中文")
+
+    def test_truncates_before_pad_when_too_long(self) -> None:
+        long = "x" * 80
+        got = _pad_display_right(long, 8)
+        assert _text_display_width(got) == 8
+        assert got.endswith("…")
+
+
+class TestPrintSessionsTable:
+    """Smoke + fixed-clock integration so Last Active is deterministic."""
+
+    def test_with_titles_prints_header_and_row(self, capsys) -> None:
+        fixed_now = 1_700_000_000.0
+        with patch("hermes_cli.main._time.time", return_value=fixed_now):
+            print_sessions_table(
+                [
+                    {
+                        "title": "Rust 项目",
+                        "preview": "分析当前",
+                        "last_active": fixed_now - 400,
+                        "id": "20260415_testsession",
+                    }
+                ],
+                has_titles=True,
+            )
+        out = capsys.readouterr().out
+        assert "Title" in out and "Preview" in out and "Last Active" in out
+        assert "Rust 项目" in out
+        assert "20260415_testsession" in out
+        assert "6m ago" in out
+        lines = [ln for ln in out.splitlines() if ln.strip()]
+        assert len(lines) >= 3
+
+    def test_without_titles_includes_source(self, capsys) -> None:
+        fixed_now = 1_700_000_000.0
+        with patch("hermes_cli.main._time.time", return_value=fixed_now):
+            print_sessions_table(
+                [
+                    {
+                        "preview": "hello",
+                        "last_active": fixed_now - 90,
+                        "source": "cli",
+                        "id": "id_only",
+                    }
+                ],
+                has_titles=False,
+            )
+        out = capsys.readouterr().out
+        assert "Preview" in out and "Src" in out
+        assert "cli" in out and "id_only" in out
+
+    def test_indent_prefix(self, capsys) -> None:
+        fixed_now = 1_700_000_000.0
+        with patch("hermes_cli.main._time.time", return_value=fixed_now):
+            print_sessions_table(
+                [{"title": "t", "preview": "p", "last_active": fixed_now, "id": "i"}],
+                has_titles=True,
+                indent="  ",
+            )
+        out = capsys.readouterr().out
+        for line in out.splitlines():
+            if line.strip():
+                assert line.startswith("  ")
+
+    def test_row_columns_have_expected_display_widths(self) -> None:
+        """Guardrail: titled row layout matches fixed column budgets + spaces."""
+        title = _pad_display_right("ColdStore Rust 项目", 32)
+        preview = _pad_display_right("分析当前项目", 40)
+        last = _pad_display_right("6m ago", 13)
+        sid = "20260415_081027_6b979d"
+        line = f"{title} {preview} {last} {sid}"
+        assert _text_display_width(title) == 32
+        assert _text_display_width(preview) == 40
+        assert _text_display_width(last) == 13
+        # Single space between padded columns, then unbounded id.
+        assert line == f"{title} {preview} {last} {sid}"
+