Add two new sections to the Pallas documentation:
- Sampling parameters: explain that temperature/top_p/top_k are
configured via the fast-agent decorator's `request_params`, with a
provider support matrix and a note on Claude Opus 4.7 stripping these
params in favor of `output_config.effort`.
- Metrics: document the Prometheus `/metrics` endpoint exposed on the
registry port, including scrape config, full metrics reference table,
and notes on where each metric is captured.
Make Pallas truly stateless per the 'Pallas is ephemeral' contract.
BREAKING (behavioural, not API):
* instance_scope changes from 'shared' to 'request' in pallas.server.
Each MCP tools/call now acquires a freshly-created fast-agent instance
via the existing create_instance / dispose_instance factories and
disposes it immediately after the response.
With 'shared' mode:
* Every MCP caller saw the same agent.message_history, so different
Daedalus conversations leaked into each other.
* Mid-chat context was silently truncated once the model window filled.
* Restarting the Pallas process wiped all in-flight conversation state,
even though Daedalus had it persisted in Postgres.
With 'request' mode the Pallas process holds no per-conversation state;
the caller (Daedalus) owns history and reseeds it on every turn.
send_message gains two optional arguments:
* history: list[{role, content, images?}] in chronological order,
converted to PromptMessageExtended and seeded onto the fresh
instance's message_history before agent.send().
* conversation_id: opaque string, logged for trace correlation only —
Pallas never interprets or persists it.
Malformed history entries (bad role, missing image data/mime_type, etc.)
are skipped with a warning rather than raising, so a single bad row
cannot wipe a whole conversation.
The {agent}_history MCP prompt is still registered under 'request'
scope for backward compatibility but always returns []; history lives
on the client.
Version bumped to 0.2.0.
