chore(ts-as-modality): M1-complete build checkpoint + resume note

Record resume state for build phase:
- M1 (T1.1-T1.7) complete; 51 tests pass; branch feature/20260629/ts-as-modality
- next: T2.1 (TS Encoder), blocked on M2 env decision (CPU vs CUDA torch)
- handoff/build-checkpoint.json captures blocker + resume instructions

openspec/changes/ts-as-modality/.comet/handoff/build-checkpoint.json

@@ -0,0 +1,31 @@
+{
+  "change": "ts-as-modality",
+  "phase": "build",
+  "checkpoint": "M1-complete",
+  "date": "2026-06-29",
+  "status": "paused-awaiting-user-decision",
+  "summary": "M1 (data pipeline) fully complete (T1.1-T1.7). 51 tests passing. All committed on feature/20260629/ts-as-modality.",
+  "next_action": "T2.1 (TS Encoder, model/ts_encoder.py). Blocked on environment setup decision for M2-M5.",
+  "blocker": {
+    "reason": "venv (.venv) has only M1 deps (numpy/tqdm/pyyaml/pytest). M2+ requires torch + transformers (+peft/accelerate/datasets for M3/M4). System torch is CPU-only; design assumes 3060 12GB GPU but actual is Quadro RTX 3000 6GB.",
+    "decision_pending": "User must choose: A) CPU torch now (M2 correctness only, no GPU mem validation); B) CUDA torch for 6GB Quadro (enables real training, expect OOM-fallbacks earlier vs 12GB plan); C) user sets up env themselves.",
+    "recommendation": "B"
+  },
+  "resume_instructions": {
+    "verify_state": "Run: /bin/bash .claude/skills/comet/scripts/comet-state.sh check ts-as-modality build",
+    "find_next_task": "grep -n '\\- \\[ \\]' openspec/changes/ts-as-modality/tasks.md | head -1  (expect T2.1)",
+    "venv": "Use .venv/bin/python for all python commands",
+    "branch": "feature/20260629/ts-as-modality",
+    "build_mode": "executing-plans",
+    "tdd_mode": "tdd",
+    "review_mode": "standard",
+    "isolation": "branch"
+  },
+  "completed_milestones": ["M1"],
+  "completed_tasks": ["1.1", "1.2", "1.3", "1.4", "1.5", "1.6", "1.7"],
+  "test_count": 51,
+  "git": {
+    "m1_complete_commit": "bbc60f2",
+    "base_ref": "7a5a1d033fb1ac20af25a17a571b2791694bd923"
+  }
+}