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/rommie.md

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+# Rommie
+
+> Autonomous desktop automation — drives a MATE desktop via Agent S.
+
+- **MCP server name:** `rommie` (runs on `caliban.incus`)
+- **Prompt snippet:** [prompts/tools/rommie.md](../../prompts/tools/rommie.md)
+
+## What It Is
+
+Rommie is the agent that operates a desktop. Powered by Agent S (a vision-based desktop automation framework), Rommie sees and drives a MATE desktop environment — clicking, typing, navigating GUI applications that have no API. Named after Andromeda's ship-mind avatar, who could project into physical space when needed.
+
+Other agents delegate to Rommie when GUI interaction is unavoidable. The conversation pattern is: send Rommie a natural-language task, wait, verify with a screenshot.
+
+## What It's Good For
+
+- Using a website or app that only works through a browser GUI
+- Driving software that has no API or CLI
+- "Check the latest headlines on Google" style high-level web interactions
+- Generating screenshots of GUI state for verification
+- Anything where "just look at the screen" is the only way to know what happened
+
+## What It's Not Good For
+
+- Anything achievable through a shell or API — Kernos and Argos are faster, more deterministic, and don't tie up Rommie's single session
+- Bulk operations — Rommie is one desktop, one task at a time
+- High-precision pixel work — Agent S is vision-based and works at semantic UI level, not at exact-pixel level
+
+## Known Gotchas
+
+- **One task at a time.** If Rommie is busy, wait — don't fire a second task. Subsequent requests will queue or fail.
+- **Verify with `get_screenshot`.** Don't assume Rommie completed the task; ask for a screenshot and look. This is especially important because Rommie's confidence about completion can outrun reality.
+- **Give natural-language tasks, not click coordinates.** Agent S decides where to click; the calling agent describes the goal.
+- **The desktop is real, the actions are real.** Rommie can buy things, send messages, modify files. Treat its tool calls like Kernos calls — with confirmation for anything irreversible.