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/layer1-budget.en.svg

@@ -0,0 +1,50 @@
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+      <stop offset="0%" stop-color="#1e3a5f"/><stop offset="100%" stop-color="#2563eb"/>
+    </linearGradient>
+    <marker id="arrow" viewBox="0 0 10 10" refX="10" refY="5" markerWidth="6" markerHeight="6" orient="auto-start-reverse">
+      <path d="M 0 0 L 10 5 L 0 10 z" fill="#16a34a"/>
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+  <rect x="0" y="0" width="720" height="38" fill="url(#header)" rx="8"/>
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+  <text x="360" y="25" fill="#fff" font-size="14" font-weight="700" text-anchor="middle">L3: toolResultBudget — Large Result Persistence</text>
+
+  <!-- Pain Point -->
+  <rect x="20" y="54" width="680" height="42" rx="6" fill="#fef2f2" stroke="#fca5a5" stroke-width="1"/>
+  <text x="35" y="72" fill="#991b1b" font-size="11" font-weight="600">Pain Point</text>
+  <text x="105" y="72" fill="#991b1b" font-size="11">Model read 30 files in one turn; total tool_result adds up to 500KB, filling the entire context window</text>
+
+  <!-- Before -->
+  <text x="155" y="118" fill="#64748b" font-size="12" font-weight="600" text-anchor="middle">Before</text>
+  <rect x="20" y="128" width="270" height="82" rx="6" fill="#fff" stroke="#94a3b8" stroke-width="1"/>
+  <text x="35" y="148" fill="#475569" font-size="10" font-family="monospace">tool_result: (78KB)  ...</text>
+  <text x="35" y="164" fill="#475569" font-size="10" font-family="monospace">tool_result: (142KB) ...</text>
+  <text x="35" y="180" fill="#475569" font-size="10" font-family="monospace">tool_result: (290KB) ...</text>
+  <text x="155" y="202" fill="#ef4444" font-size="9" font-weight="600" text-anchor="middle">Total 510KB → over budget</text>
+
+  <!-- Arrow -->
+  <line x1="295" y1="163" x2="360" y2="163" stroke="#16a34a" stroke-width="2" marker-end="url(#arrow)"/>
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+  <text x="485" y="118" fill="#16a34a" font-size="12" font-weight="600" text-anchor="middle">After</text>
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+  <text x="380" y="148" fill="#166534" font-size="10" font-family="monospace">tool_result: &lt;persisted-output&gt;</text>
+  <text x="395" y="164" fill="#166534" font-size="9">Full output: .task_outputs/t1.txt</text>
+  <text x="395" y="178" fill="#166534" font-size="9">Preview: (first 2000 chars) ...</text>
+  <text x="532" y="202" fill="#16a34a" font-size="9" font-weight="600" text-anchor="middle">Total 18KB → normal</text>
+
+  <!-- How it works -->
+  <rect x="20" y="214" width="680" height="64" rx="6" fill="#f8fafc" stroke="#cbd5e1" stroke-width="1"/>
+  <text x="35" y="234" fill="#1e3a5f" font-size="11" font-weight="600">How</text>
+  <text x="70" y="234" fill="#475569" font-size="10">1. Sum the size of all tool_result in the latest turn</text>
+  <text x="70" y="250" fill="#475569" font-size="10">2. Over 200KB → sort by size, persist the largest to .task_outputs/tool-results/</text>
+  <text x="70" y="266" fill="#475569" font-size="10">3. Keep only &lt;persisted-output&gt; marker + first 2000 chars preview in context</text>
+
+  <!-- Result summary -->
+  <rect x="20" y="290" width="680" height="36" rx="6" fill="#f0fdf4" stroke="#16a34a" stroke-width="1"/>
+  <text x="35" y="312" fill="#166534" font-size="11">Result: No data lost (full data on disk), context drops from 510KB to ~18KB, 0 API calls</text>
+</svg>