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/tools/context7.md

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+# Context7
+
+> Library and framework documentation lookup.
+
+- **MCP server name:** `context7` (runs locally via npx)
+- **Prompt snippet:** [prompts/tools/context7.md](../../prompts/tools/context7.md)
+
+## What It Is
+
+Context7 is a purpose-built MCP server for fetching current library, framework, SDK, API, and CLI documentation. It returns structured, version-aware results — meaningfully better than Argos for "how does this library work" type questions.
+
+## What It's Good For
+
+- API syntax, method signatures, configuration options for libraries
+- Framework setup instructions and patterns (Django, React, Next.js, Tailwind, FastAPI, etc.)
+- CLI tool usage and flags
+- Version migration guides
+- Library-specific debugging — "why does this configuration fail"
+
+Use Context7 even for well-known libraries — training data may be stale on recent releases.
+
+## What It's Not Good For
+
+- Refactoring or writing scripts from scratch — Context7 documents, doesn't implement
+- General programming concepts — Context7 indexes libraries, not theory
+- Code review — use the agent's own judgment, not external docs
+- Business logic debugging — Context7 won't know your code
+
+## Known Gotchas
+
+- **Resolve the library ID first.** Context7 typically expects a library identifier; `resolve-library-id` style calls precede `query-docs` calls.
+- **Version matters.** When library behavior is version-specific, include the version in the query. The doc index may have multiple versions.
+- **Prefer over web search for libraries.** When the question is "how does X library work," Context7 is the right first stop. Argos is the fallback.