Follow up PR #265: refine chapters, diagrams, and add S20 (#283)

* feat: s01-s14 docs quality overhaul — tool pipeline, single-agent, knowledge & resilience

Rewrite code.py and README (zh/en/ja) for s01-s14, each chapter building
incrementally on the previous. Key fixes across chapters:

- s01-s04: agent loop, tool dispatch, permission pipeline, hooks
- s05-s08: todo write, subagent, skill loading, context compact
- s09-s11: memory system, system prompt assembly, error recovery
- s12-s14: task graph, background tasks, cron scheduler

All chapters CC source-verified. Code inherits fixes forward (PROMPT_SECTIONS,
json.dumps cache, real-state context, can_start dep protection, etc.).

* feat: s15-s19 docs quality overhaul — multi-agent platform: teams, protocols, autonomy, worktree, MCP tools

Rewrite code.py and README (zh/en/ja) for s15-s19, the multi-agent platform
chapters. Each chapter inherits all previous fixes and adds one mechanism:

- s15: agent teams (TeamCreate, teammate threads, shared task list)
- s16: team protocols (plan approval, shutdown handshake, consume_inbox)
- s17: autonomous agents (idle polling, auto-claim, consume_lead_inbox)
- s18: worktree isolation (git worktree, bind_task, cwd switching, safety)
- s19: MCP tools (MCPClient, normalize_mcp_name, assemble_tool_pool, no cache)

All appendix source code references verified against CC source. Config priority
corrected: claude.ai < plugin < user < project < local.

* fix: 5 regressions across s05-s19 — glob safety, todo validation, memory extraction, protocol types, dep crash

- s05-s09: glob results now filter with is_relative_to(WORKDIR) (inherited from s02)
- s06-s08: todo_write validates content/status required fields (inherited from s05)
- s09: extract_memories uses pre-compression snapshot instead of compacted messages
- s16: submit_plan docstring clarifies protocol-only (not code-level gate)
- s17-s19: match_response restores type mismatch validation (from s16)
- s17-s19: claim_task deps list handles missing dep files without crashing

* fix: s12 Todo V2 logic reversal, s14/s15 cron range validation, s18/s19 worktree name validation

- s12 README (zh/en/ja): fix Todo V2 direction — interactive defaults to Task,
  non-interactive/SDK defaults to TodoWrite. Fix env var name to
  CLAUDE_CODE_ENABLE_TASKS (not TODO_V2).
- s14/s15: add _validate_cron_field with per-field range checks (minute 0-59,
  hour 0-23, dom 1-31, month 1-12, dow 0-6), step > 0, range lo <= hi.
  Replace old try/except validation that only caught exceptions.
- s18/s19: add validate_worktree_name() to remove_worktree and keep_worktree,
  not just create_worktree.

* fix: align s16-s19 teaching tool consistency

* fix pr265 chapter diagrams

* Add comprehensive s20 harness chapter

* Fix chapter smoke test regressions

* Clarify README tutorial track transition

---------

Co-authored-by: Haoran <bill-billion@outlook.com>

s08_context_compact/images/micro-compact.en.svg

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+  <text x="360" y="25" fill="#fff" font-size="14" font-weight="700" text-anchor="middle">L2: microCompact — Old Result Placeholder Replacement</text>
+
+  <!-- Pain Point -->
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+  <text x="35" y="70" fill="#991b1b" font-size="11" font-weight="600">Pain Point</text>
+  <text x="110" y="70" fill="#991b1b" font-size="11">Agent read 10 files in a row; the full content of reads 1-7 is still sitting in context, taking space but no longer useful</text>
+
+  <!-- Before -->
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+  <text x="38" y="153" fill="#94a3b8" font-size="8" font-family="monospace">Read file B: (full content, 1800 chars)...</text>
+  <rect x="30" y="160" width="290" height="10" rx="2" fill="#e2e8f0"/>
+  <text x="38" y="168" fill="#94a3b8" font-size="8" font-family="monospace">Read file C: (full content, 4500 chars)...</text>
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+  <text x="175" y="212" fill="#ef4444" font-size="9" font-weight="600">7 old results waste ~25K chars</text>
+
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+  <text x="408" y="138" fill="#92400e" font-size="8" font-family="monospace">[Earlier result compacted. Re-run if needed.]</text>
+  <rect x="400" y="145" width="290" height="10" rx="2" fill="#fef3c7"/>
+  <text x="408" y="153" fill="#92400e" font-size="8" font-family="monospace">[Earlier result compacted. Re-run if needed.]</text>
+  <rect x="400" y="160" width="290" height="10" rx="2" fill="#fef3c7"/>
+  <text x="408" y="168" fill="#92400e" font-size="8" font-family="monospace">[Earlier result compacted. Re-run if needed.]</text>
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+</svg>