feat(layout): reduce default MAM_MIN_PANE_COLS to 40 for single workspace 2xK multi-pane tiling

.agents/reports/reviewer-cline-01/report-bb360685.md

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+# Review Report — Job bb360685
+
+- **Reviewer**: cline (herdr session `reviewer-cline-01`, role: reviewer)
+- **Job ID**: bb360685
+- **Reviewed branch**: `refactor` (changes unstaged in working tree)
+- **Scope**: Cross code review (lint / operability / drift) of the diff for
+  "Improve 2xK grid layout engine and prevent premature workspace overflow".
+- **Diff stat**: 7 files, +236 / -9 (plus a dirty submodule).
+
+## 1. Change Inventory
+
+| File | Change | Category |
+|------|--------|----------|
+| `.agents/skills/lib_py/layout.py` | `compute_2xk_layout` default `min_cols` 60→40; CLI `--min-cols` default 60→40; `_env_int` docstring 60→40 | Core logic (task goal #1, #2) |
+| `.agents/skills/lib.sh:432` | Fallback `${MAM_MIN_PANE_COLS:-60}` → `:-40` | Core logic (task goal #1) |
+| `.mam.env.example` | Documented default `MAM_MIN_PANE_COLS` 60→40 | Config/docs (task goal #1) |
+| `tests/test_layout.py` | Updated lib.sh snippet expectation (`:-60`→`:-40`); J-1 docstring 60→40; +4 new tests (default-40, 80-col boundary, 90/100-col tiling) | Tests (task goal #3) |
+| `tests/test_tier1_unit.py` | +2 new Tier-1 tests (default-40, 90/100-col tiling) | Tests (task goal #3) |
+| `tests/test_a4_adapter_contract.py` | Widened `claude` `ready_tokens` regex (`+|Claude Code|Opus|Sonnet|Haiku`) | **Unrelated to layout task** |
+| `nats-docker` (submodule) | `PRIVATE_SERVER.md` modified → submodule marked `-dirty` | **Stray / drift, unrelated** |
+
+## 2. Lint / Syntax
+
+- `python -m py_compile lib_py/layout.py` → **OK**
+- `bash -n .agents/skills/lib.sh` → **OK**
+- No leftover `MAM_MIN_PANE_COLS:-60` fallbacks anywhere in `.sh`/`.py`. The only
+  remaining `60` references are *explicit* `min_cols=60` arguments in pre-existing
+  layout tests (legitimate — they exercise the 60 configuration, not the default)
+  and one contrast docstring line. The default is consistently 40 across all three
+  authoritative sites (function signature, CLI argparse, lib.sh fallback) and the
+  env example. **No orphans.**
+
+## 3. Operability — Goal-by-Goal Verification
+
+### Goal #1 — Default 60→40 to enable 3-4 agents in ~100-col windows
+- Verified all three default sites are 40 and consistent.
+- Practical effect: with `min_cols=60`, a 100-col pane split right yields 50-col
+  halves → `50 < 60` → immediate `column_width_overflow` (could not even open a
+  2nd column). With `min_cols=40`, `50 >= 40` → 2 columns (4 panes) fit before
+  overflow. The change materially enables 3-4 agents per ~100-col workspace, not
+  merely cosmetic. ✓
+
+### Goal #2 — Clean 2-column split at width >= 80 without premature overflow
+- Boundary predicate is `rightmost_top_pane.width // 2 < min_cols` (strict `<`).
+  At width 80: `80//2 = 40`, `40 < 40` is **False** → splits right (not overflow).
+  At width 79: `79//2 = 39`, `39 < 40` is **True** → `column_width_overflow`.
+- CLI end-to-end confirmation (mirrors the `lib.sh` invocation path):
+  - 80-col payload → `right p1` ✓
+  - 79-col payload → `overflow p1` ✓
+- The boundary is exactly at 80 and behaves as specified. ✓
+
+### Goal #3 — Updated unit tests assert default 40 & 90-100 col tiling
+- New tests present in both suites:
+  - `test_default_min_cols_is_40` / `test_layout_default_min_cols_40_in_tier1`
+  - `test_80_col_2_column_splitting_boundary`
+  - `test_90_col_single_workspace_multi_pane_tiling` /
+    `test_100_col_single_workspace_multi_pane_tiling` /
+    `test_layout_single_workspace_90_100_cols_tiling_tier1`
+- Tiling tests verify the full 1→2→3→4→(5th overflow) progression with correct
+  target panes and `column_width_overflow` reason. Traced the column-grouping
+  logic: singleton-column fill at step 3→4 and width-constrained overflow at
+  step 4→5 are both reached correctly. ✓
+
+### Goal #4 — Full pytest suite passes
+- Targeted run of the three affected unit-test files:
+  `tests/test_layout.py tests/test_tier1_unit.py tests/test_a4_adapter_contract.py`
+  → **99 passed in 10.97s**. ✓
+- The complete `pytest tests/` suite could not be fully executed within this
+  review's time budget (integration tests are long-running), but every file
+  touched by the diff passes, and no unit-test regression is introduced.
+
+## 4. Findings (advisory, non-blocking)
+
+### F-1 (Hygiene/Scope): `test_a4_adapter_contract.py` change is out of scope
+- The `claude` `ready_tokens` regex widening (`+|Claude Code|Opus|Sonnet|Haiku`)
+  is a correct, additive adapter fix and the contract test passes — but it is
+  **unrelated** to the 2xK layout-engine task. Bundling it into this diff blurs
+  traceability.
+- **Direction**: Split into its own commit (`fix(adapter): broaden claude
+  ready_tokens`) before merging. No code change required for the layout work.
+
+### F-2 (Drift): `nats-docker` submodule is dirty
+- `git diff nats-docker` shows the submodule pointer unchanged but flagged
+  `-dirty`; `git -C nats-docker status` shows ` M PRIVATE_SERVER.md`.
+- This is a stray local modification inside the submodule, unrelated to the
+  task, and risks being accidentally staged/committed alongside the layout
+  changes.
+- **Direction**: Revert the stray edit (`git -C nats-docker checkout --
+  PRIVATE_SERVER.md`) or leave the submodule unstaged. Do not commit the
+  submodule pointer change with this work.
+
+## 5. Summary
+
+The core implementation correctly and consistently lowers the 2xK layout
+`min_cols` default from 60 to 40 across `lib.sh`, `layout.py` (function +
+CLI + docstring), and `.mam.env.example`, with matching, passing unit tests
+covering the 80-col boundary and 90/100-col single-workspace tiling. Syntax
+and CLI operability are verified. The two findings (F-1 out-of-scope adapter
+regex, F-2 dirty submodule) are hygiene/drift items that do not affect the
+layout engine's correctness or operability and require only commit
+housekeeping, not a redesign.
+
+[VERDICT: PASS]