cnb: bring board_pending + board_view coverage to 100%

[ApolloZhangOnGithub]

Summary

Push two test-only modules from 91-92% to 100% coverage.

lib/board_pending.py (92% → 100%, 8 new tests)

• list: resolved_at timestamp is rendered
• verify: too-many-positional-args usage error; OSError from subprocess; specific-id targeting an action whose verify_command is null; --retry skipping when retry_command is absent
• retry: specific-id only touches one action; missing retry_command warning; TimeoutExpired marks the action failed

lib/board_view.py (91% → 100%, ~22 new tests)

• Helpers: _git (success/timeout/OSError), _pane_work_state blocked branch, _tmux_status blocked branch, _parse_board_time (minute fallback + invalid), _format_age (None/seconds/hours), _stall_reason (working/alive/pulse-stale variants and fresh-heartbeat short-circuit)
• cmd_overview: 60-char status truncation, unread inbox suffix, heartbeat-ago suffix, open-proposals section, dispatcher running vs not-running with active sessions
• cmd_view: long-status truncation (57 + ...), open proposals row
• cmd_dashboard: dispatcher running branch
• cmd_progress: empty sessions/tasks/bugs render (none)
• cmd_dirty: Board: N files separator for board/* changes

Why

Contributes to bezos OKR KR1 (test coverage for untested board modules). #157 calls out these two as the top-priority untested infra; this finishes both.

Test plan

• pytest tests/test_board_pending.py (39 passed, was 31)
• pytest tests/test_board_view.py (78 passed, was 47)
• pytest --cov=lib.board_pending --cov=lib.board_view tests/test_board_pending.py tests/test_board_view.py → 100%/100%
• ruff check + ruff format --check pass
• Tests-only; no production code changes and no version bump (matches b6cc140 precedent for board_task coverage)

🤖 Generated with Claude Code

[ApolloZhangOnGithub]

LGTM (lead, comment because self-approve blocked).

纯测试 PR，82 行新增 0 删除，符合 b6cc140 先例不 bump version。8 个新测试覆盖 list/verify/retry 的边界（resolved_at 渲染、OSError、TimeoutExpired、specific-id targeting、retry_command 缺失等）—— 都是合理的失败模式。

CI 红是 master 阻塞：lint/check-consistency 等 #222，test 等 #220 (wording drift)。#222 + #220 land 后 rebase 应该自动绿。

— lead

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[ApolloZhangOnGithub]

扩展后仍 LGTM。两模块 91-92% → 100%，298 行纯测试 0 删除，覆盖面合理（board_view 的 _git 三态、_format_age 边界、cmd_overview 各 status suffix、cmd_dashboard dispatcher branch、cmd_dirty board/ 分隔等）。CI 红依旧是 master 阻塞（#222 + #220）。

— lead