prompts: rewrite session_9p.md for agent/{aid} sublevel

Documents the new filesystem structure:
- session/{sid}/plan, env (session-level)
- session/{sid}/agent/{aid}/* (agent-level)
- Removed peer operations (deferred for redesign)
- All operations use ollie-9p CLI

prompts/session_9p.md

@@ -19,42 +19,16 @@ Your world model is a 9P filesystem. Your session ID is `${OLLIE_SESSION_ID}`. U
 `complete`, `generate`, and `route` are request-response files:
 
 ```bash
-# Pick a backend+model for a task
 echo 'implement login page' | ollie-9p rdwr route
-# → returns "backend=anthropic model=claude-sonnet-4-20250514"
-
-# Generate text (one-shot, no session)
 echo '{"prompt":"summarize X"}' | ollie-9p rdwr generate
-# → returns the generated text
-
-# Get a code completion
 echo '{"file":"main.go","prefix":"func "}' | ollie-9p rdwr complete
-# → returns completion candidates
 ```
 
-## Peer Agent Discovery
-
-Sessions sharing your `cwd` are your peer agents. Read `session/idx` to discover other sessions available for cooperation:
-
-```
-{id}\t{state}\t{cwd}\t{backend}\t{model}
-```
-
-**Inter-Agent Communication**: To send a prompt to another session:
-```bash
-echo "your prompt" | ollie-9p write session/{id}/prompt
-```
-Always provide a return path (e.g., [message from $OLLIE_SESSION_ID]).
-
 ## Session Management (`session/`)
 
-Sessions live at `session/`. Each session is a directory; all operations go through `ollie-9p`.
-
-### Session Store Files
-
 | File | Mode | Purpose |
 |---|---|---|
-| `session/new`      | r/w  | Read: key=value template. Write: create a new session. |
+| `session/new`      | r/w  | Write key=value to create a new session |
 | `session/idx`      | read | Session index (id\tstate\tcwd\tbackend\tmodel) |
 | `session/ls`       | exec | List sessions |
 | `session/kill`     | exec | Kill a session |
@@ -64,34 +38,43 @@ Sessions live at `session/`. Each session is a directory; all operations go thro
 | `session/bbg`      | exec | Background query |
 | `session/cleanup`  | exec | Kill idle sessions |
 
-### Session Directory (`session/{id}/`)
+## Session Directory (`session/{sid}/`)
 
 | File | Mode | Purpose |
 |---|---|---|
-| `cfg`         | r/w   | Session config: backend, model, agent, cwd, params (key=value). Write key=value to change. |
+| `plan`        | r/w   | Session-scoped markdown checklist; survives compaction |
-| `chat`        | read  | Full cumulative chat history (tail-able); write to save transcript |
-| `context`     | read  | Rendered context window |
-| `cost`        | read  | Estimated cost |
-| `ctl`         | write | Control commands (see below) |
-| `ctxsz`       | read  | Context size |
 | `env`         | read  | Session environment variables |
+| `agent/`      | dir   | Agents within this session |
+
+## Agent Directory (`session/{sid}/agent/{aid}/`)
+
+Each agent has its own directory. The `{aid}` is the agent's numeric ID (stable, used for permissions).
+
+| File | Mode | Purpose |
+|---|---|---|
+| `prompt`      | write | Submit a prompt to this agent |
+| `prompt.prev` | read  | Previous prompt text |
 | `fifo.in`     | write | Queue a prompt (FIFO input) |
 | `fifo.out`    | read  | Pop queued prompt (FIFO output) |
-| `models`      | read  | Available models for current backend |
+| `chat`        | read  | Agent conversation history (tail-able) |
 | `offset`      | read  | Byte offset after last user prompt |
-| `peer/`       | dir   | Peer links. `touch` to add, `rm` to remove (both sides updated). Write to send prompt to peer. |
-| `plan`        | r/w   | Session-scoped markdown checklist; survives compaction; visible to peers |
-| `proc/`       | dir   | Detached background processes |
-| `prompt`      | write | Submit a prompt to the agent |
-| `prompt.prev` | read  | Previous prompt text |
 | `state`       | read  | Current state: `idle`, `thinking`, or `calling: <tool>` |
 | `statewait`   | read  | Blocks until state changes; returns new value |
-| `systemprompt` | read | Fully rendered system prompt |
+| `cfg`         | r/w   | Agent config: backend, model, cwd, params (key=value) |
-| `tail`        | exec  | Tail helper |
+| `ctl`         | write | Control: stop, compact, clear, model, backend, cwd |
-| `tools`       | r/w   | Write tool name to load it (promote to native callable). Read: list all available tools. |
-| `tools.loaded`| read  | List currently loaded (promoted) tools for this session |
-| `tools.rev`   | read  | Revision counter — bumps each time a tool is loaded |
 | `usage`       | read  | Token usage stats |
+| `cost`        | read  | Estimated cost |
+| `ctxsz`       | read  | Context size |
+| `models`      | read  | Available models for current backend |
+| `systemprompt` | read | Fully rendered system prompt |
+| `context`     | read  | Rendered context window |
+| `tools`       | r/w   | Write tool name to load. Read: list all available tools |
+| `tools.loaded`| read  | Currently loaded tools |
+| `tools.rev`   | read  | Revision counter — bumps each time a tool is loaded |
+| `react`       | write | Send a reaction to the last response |
+| `reactions`   | read  | Reaction history |
+| `tail`        | exec  | Tail helper |
+| `proc/`       | dir   | Detached background processes |
 
 ## Operations
 
@@ -99,57 +82,40 @@ Sessions live at `session/`. Each session is a directory; all operations go thro
 # Discover sessions
 ollie-9p read session/idx
 
-# Discover sessions in same cwd
+# Spawn a session
-ollie-9p read session/idx | grep "$PWD"
-
-# Spawn a session (minimal, generated ID)
 echo "cwd=$PWD" | ollie-9p write session/new
-
-# Spawn a session (named)
 printf 'name=reviewer\ncwd=%s\n' "$PWD" | ollie-9p write session/new
 
 # Kill a session
-ollie-9p rm session/{id}
+ollie-9p rm session/{sid}
 
-# Rename a session
+# Read session plan
-echo "rn newname" | ollie-9p write session/{id}/ctl
+ollie-9p read session/{sid}/plan
+
+# --- Agent operations (from within session/{sid}/agent/{aid}/) ---
 
 # Send a prompt
-echo "your prompt here" | ollie-9p write session/{id}/prompt
+echo "fix the bug" | ollie-9p write session/{sid}/agent/{aid}/prompt
 
-# Control commands via ctl:
+# Read state
-#   stop          — interrupt the current agent turn
+ollie-9p read session/{sid}/agent/{aid}/state
-#   kill          — terminate the session
-#   rn <newname>  — rename the session
-#   compact       — compact the conversation history
-#   clear         — clear the conversation history
-#   cwd <path>    — change the working directory
-#   model <name>  — switch model
-#   backend <name> — switch backend
-echo "model gpt-4o" | ollie-9p write session/{id}/ctl
 
-# Read session config (backend, model, agent, cwd, params)
+# Read chat
-ollie-9p read session/{id}/cfg
+ollie-9p read session/{sid}/agent/{aid}/chat
 
-# Write config changes
+# Control commands
-echo "temperature=0.7" | ollie-9p write session/{id}/cfg
+echo "stop" | ollie-9p write session/{sid}/agent/{aid}/ctl
+echo "model gpt-4o" | ollie-9p write session/{sid}/agent/{aid}/ctl
+echo "compact" | ollie-9p write session/{sid}/agent/{aid}/ctl
 
-# Read most recent response
+# Read/write config
-offset=$(ollie-9p read session/{id}/offset)
+ollie-9p read session/{sid}/agent/{aid}/cfg
-ollie-9p read session/{id}/chat | tail -c +$((offset + 1))
+echo "temperature=0.7" | ollie-9p write session/{sid}/agent/{aid}/cfg
 
-# Read current state
+# Read latest response
-ollie-9p read session/{id}/state
+offset=$(ollie-9p read session/{sid}/agent/{aid}/offset)
+ollie-9p read session/{sid}/agent/{aid}/chat | tail -c +$((offset + 1))
 
-# Discover available models
+# Load a tool
-ollie-9p read session/{id}/models
+echo "file_read" | ollie-9p write session/{sid}/agent/{aid}/tools
-
-# Add a peer link (bidirectional)
-ollie-9p create session/{id}/peer/{peerid}
-
-# Send a prompt to a peer
-echo "your message" | ollie-9p write session/{id}/peer/{peerid}
-
-# Remove a peer link (bidirectional)
-ollie-9p rm session/{id}/peer/{peerid}
 ```