feat: add conversation with grounded replies, sample mind and M1 acceptance test

Phase 8, completing milestone M1. A user message is stored and appended
as an observation event carrying trust, actor, channel and reference. The
perceive process analyses it deterministically (intent, introspection
kind, entities, claims, urgency) and, within the per-cycle model
allowance, enriches it through the perceive prompt. Its handler writes a
perception event, an episodic memory with participants, turns claims into
beliefs whose evidence is the message, and builds a response intent from
state: beliefs and memories for the topic, evidence rows for why-questions,
the uncertain band, contested beliefs and their links, recent learning,
status changes, and honest declines for subsystems that do not exist yet
or for requests with no capabilities. The respond prompt phrases the
intent when a model is assigned; otherwise the reply is a direct
rendering of the intent. response_generated cites the message, the
perception, every belief and memory used, the episode and the model call.

API: conversations, messages with optional wait, one-shot ask; chat UI
with live refresh and a per-reply intent view. Sample mind Dani as a
strictly decoded seed document with an import endpoint and noemactl mind
import. tests/m1 drives all fourteen milestone steps including restart.

internal/brain/process.go

@@ -6,6 +6,7 @@ package brain
 
 import (
 	"context"
+	"sync/atomic"
 	"time"
 
 	"github.com/andydixon/noema/internal/attention"
@@ -65,6 +66,21 @@ type State struct {
 	NewEvents []events.Event  // since the last cycle, ascending
 	Workspace workspace.State // snapshot before this cycle
 	Services  Services
+	llmCalls  atomic.Int32 // model calls made in this cycle; processes and handlers share the cap
+}
+
+// AllowLLM reserves one model call against the mind's per-cycle cap and
+// reports whether it was granted, so a chatty cycle cannot exceed the budget.
+func (s *State) AllowLLM() bool {
+	cap := int32(s.Mind.Config.LLMCallsPerCycle)
+	if cap <= 0 || s.Services.LLM == nil {
+		return false
+	}
+	if s.llmCalls.Add(1) > cap {
+		s.llmCalls.Add(-1)
+		return false
+	}
+	return true
 }
 
 // Services are read handles processes may use. Extended per phase.