Writing to session/{s}/agent/new with a prompt= key now blocks
until the agent completes its task, then returns the reply and
destroys the transient agent. Without prompt=, behaves as before
(creates agent, returns ID).
Also:
- Move ParsePayload/UnescapeValue to shared ollie/toolsrv package
- Remove duplicate implementations from cmd/toolsrv/internal/server
- Add session.CreateAgentWithParams for direct AgentParams usage
- Eliminate flattenParams/unescapeValue redundancy in fs package
The package defines the Server type and its namespace — 'fs' was a
leftover name from when it only held the filesystem spec. Now it's
the server definition. File renamed spec.go → server.go to match.