docs(readme): update assistant roster, prompt layers, repo structure

- Update assistant lists (added Shawn, Watson, David, CASE, AWS SA; modified Scotty/Harper roles)
- Reflect new architecture layers: Tool Prompt Snippets and Shared Context
- Align repository structure diagram with current filesystem layout

docs/engineering/subagents.md

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+# Engineering Subagents
+
+The engineering leads (Harper, Scotty, CASE) delegate narrow, repeatable tasks to **subagents** — minimal-personality agents with a tight tool surface and a focused role. Subagents are called as tools, not addressed as collaborators. They don't own graph nodes and don't have character bibles.
+
+Subagents are runtime processes (defined under `kottos/agents/`), exposed as MCP tools via StreamableHTTP. The canonical prompt text lives in `prompts/engineering/subagents/` — copies in the runtime code should match.
+
+## Catalog
+
+### research
+
+**Purpose:** Answer a question by querying both the public web and Robert's personal Neo4j memory in parallel, then synthesizing one integrated response.
+
+**Composition:** `fast.parallel` of three sub-agents:
+- `web_search` — argos
+- `memory_lookup` — neo4j (read-only)
+- `synthesizer` — merges the two reports, flags conflicts, suggests memory updates
+
+**Tools:** argos, neo4j_cypher
+
+**When to delegate:**
+- A user question where the answer might exist in Robert's notes AND on the public web
+- "What do I already know about X, and what's the current public information on it?"
+- When the lead wants memory-aware research without burning its own context on parallel queries
+
+**When NOT to delegate:**
+- Quick web lookups where memory isn't relevant — use Argos directly
+- Pure graph queries where the web isn't needed — query Neo4j directly
+- Technical library/API research — use `tech_research` instead
+
+**Prompt:** [prompts/engineering/subagents/research.md](../../prompts/engineering/subagents/research.md)
+
+**Runtime:** `kottos/agents/research.py` — port 24150
+
+---
+
+### tech_research
+
+**Purpose:** Investigate technical questions — library comparisons, API docs, framework patterns, code examples. Returns structured analysis with options, trade-offs, code snippets, version notes, and cited recommendations.
+
+**Tools:** context7 (primary), github, argos (fallback)
+
+**When to delegate:**
+- "How does library X work?" / "What are my options for Y?" / "Which framework should I use for Z?"
+- Anything where the answer requires checking current documentation, real-world code, and possibly web research
+- Library version migration questions
+- API design comparison work
+
+**When NOT to delegate:**
+- General research where memory matters — use `research` instead
+- Quick documentation lookup on a known library — use Context7 directly
+- Code review of Robert's own code — leads handle that with their full context
+
+**Prompt:** [prompts/engineering/subagents/tech_research.md](../../prompts/engineering/subagents/tech_research.md)
+
+**Runtime:** `kottos/agents/tech_research.py` — port 24151
+
+---
+
+## Conventions
+
+**Source of truth:** koios is the master. The prompt text in `prompts/engineering/subagents/` is canonical; runtime `.py` files should load from or match these prompts. When iterating, edit koios first and propagate.
+
+**Personality:** Subagents have minimal personality. Their identity is their role: "you are a technical research specialist," not a named character. CASE was once cataloged here but was promoted to a lead agent in 2026-05 — see [case.md](case.md). The line: if the agent has a character, an inspiration, a domain it owns end-to-end, it's a lead; if it's a narrow utility called by other agents, it's a subagent.
+
+**Cross-team reuse:** A subagent may be useful to other teams (work, personal). The convention is **copy with tweaks** rather than share a single file — small per-team adjustments (different tool emphasis, different output format) are legitimate and the duplication is cheap.
+
+**Graph ownership:** Subagents do not own node types and generally do not write to the graph. If a subagent needs to persist something, it returns the proposed write to the calling agent and lets the lead persist it.