feat(m1): attribute vocab + sampling (T1.2)

- ATTRIBUTE_VOCAB (16 AIOps channels w/ units)
- FREQ_BANDS (6 sampling resolutions)
- sample_attributes(n_channels, seed) -> unique-name, reproducible
- tests/test_attributes.py (8 tests, RED->GREEN)

Exit criteria: fields complete, count correct, seed-reproducible.

tests/test_attributes.py

@@ -0,0 +1,62 @@
+"""Tests for attribute vocab + sampling (T1.2)."""
+import numpy as np
+
+from tsmm.data.attributes import sample_attributes, ATTRIBUTE_VOCAB, FREQ_BANDS
+
+
+# ─── field completeness ────────────────────────────────────────────────────
+def test_each_sampled_attribute_has_required_fields():
+    attrs = sample_attributes(n_channels=4, seed=0)
+    assert len(attrs) == 4
+    for a in attrs:
+        assert set(a.keys()) >= {"name", "unit", "freq"}
+        assert isinstance(a["name"], str) and a["name"]
+        assert isinstance(a["unit"], str) and a["unit"]
+        assert isinstance(a["freq"], str) and a["freq"]
+
+
+def test_names_are_unique_within_a_sample():
+    attrs = sample_attributes(n_channels=5, seed=1)
+    names = [a["name"] for a in attrs]
+    assert len(names) == len(set(names)), "channel names must be unique"
+
+
+# ─── correctness of count ──────────────────────────────────────────────────
+def test_count_matches_request():
+    for n in (1, 2, 8):
+        assert len(sample_attributes(n_channels=n, seed=0)) == n
+
+
+def test_raises_when_request_exceeds_vocab():
+    # vocab is finite; requesting more channels than distinct names must raise.
+    import pytest
+
+    too_many = len(ATTRIBUTE_VOCAB) + 1
+    with pytest.raises(ValueError):
+        sample_attributes(n_channels=too_many, seed=0)
+
+
+# ─── reproducibility ───────────────────────────────────────────────────────
+def test_same_seed_gives_same_result():
+    a = sample_attributes(n_channels=6, seed=42)
+    b = sample_attributes(n_channels=6, seed=42)
+    assert a == b
+
+
+def test_different_seed_gives_different_result():
+    a = sample_attributes(n_channels=6, seed=1)
+    b = sample_attributes(n_channels=6, seed=2)
+    assert a != b
+
+
+# ─── vocab sanity ──────────────────────────────────────────────────────────
+def test_attribute_vocab_is_non_empty():
+    assert len(ATTRIBUTE_VOCAB) >= 6  # CPU/mem/traffic/latency/temp/rps ...
+    for entry in ATTRIBUTE_VOCAB:
+        assert "name" in entry and "unit" in entry
+
+
+def test_freq_bands_are_documented():
+    assert len(FREQ_BANDS) >= 2
+    for band in FREQ_BANDS:
+        assert isinstance(band, str) and band  # e.g. "1s", "10s", "1min"