grammar: the last two model calls that were still free text

The replier and the meeting summariser were the two call sites without a
GBNF. Both are exactly the shape that makes a Thinking variant answer with
its reasoning as prose, and neither had anything downstream that could
remove it.

The replier already parses {"response","mood"}, so it now sends the phraser's
grammar for that contract, exported once as phraser.ResponseGrammar so the
two definitions cannot drift.

The summariser stays text-in/text-out. The JSON wrapper is attached and
unwrapped in the daemon's Completer, so internal/capture is unchanged and a
Completer without a grammar still works.

The simulator told routing from phrasing by "has a grammar", which stopped
being true here; it now looks for the intent enum.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

cmd/mavend/capture.go

@@ -31,9 +31,11 @@ package main
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"log"
+	"strings"
 	"sync"
 	"time"
 
@@ -54,16 +56,65 @@ import (
 // asks Maven to stop recording gets the transcript back in seconds.
 const captureSummaryTimeout = 20 * time.Minute
 
+// summaryGrammar — GBNF pinning a summarisation call to one JSON object holding
+// the summary and nothing else. Same reasoning as responseGrammar and memeval's
+// evalGrammar: the resident model is a Thinking variant, and a summarisation
+// prompt is exactly the shape that invites it to answer with its reasoning as
+// plain text. Demanding JSON leaves the reasoning nowhere to go.
+//
+// The bound is 2000 characters, twice the phraser's, because a reduce step over
+// a two-hour meeting is a paragraph and not a sentence. Newlines are escaped by
+// the escape rule, so the bullet list the prompt asks for survives the wrapper.
+const summaryGrammar = `
+root    ::= "{" ws "\"summary\"" ws ":" ws string ws "}"
+string  ::= "\"" ([^"\\] | "\\" ["\\/bfnrt]){0,2000} "\""
+ws      ::= [ \t\n]*
+`
+
 // llmCompleter adapts *llm.Client to capture.Completer. The pure package names
 // the two strings it needs and stays free of the llm request struct; the client
 // itself is the swap-aware one from llmClientFor, so a model swap re-points it.
+//
+// The JSON wrapper lives here, not in internal/capture: that package is
+// text-in/text-out by design, and the map/reduce steps still see plain prose.
 type llmCompleter struct {
 	c         *llm.Client
 	maxTokens int
 }
 
 func (l llmCompleter) Complete(ctx context.Context, system, user string) (string, error) {
-	return l.c.Complete(ctx, llm.Req{System: system, User: user, MaxTokens: l.maxTokens})
+	out, err := l.c.Complete(ctx, llm.Req{
+		System:    system,
+		User:      user,
+		Grammar:   summaryGrammar,
+		MaxTokens: l.maxTokens,
+	})
+	if err != nil {
+		return "", err
+	}
+	return unwrapSummary(out), nil
+}
+
+// unwrapSummary takes the summary out of the JSON object the grammar produced.
+// Anything that does not parse is returned as-is: an operator running without a
+// grammar, or a llama-server too old to honour one, gets the plain text it used
+// to get rather than an empty meeting summary.
+func unwrapSummary(raw string) string {
+	s := stripThink(strings.TrimSpace(raw))
+	start := strings.Index(s, "{")
+	end := strings.LastIndex(s, "}")
+	if start < 0 || end <= start {
+		return s
+	}
+	var parsed struct {
+		Summary string `json:"summary"`
+	}
+	if err := json.Unmarshal([]byte(s[start:end+1]), &parsed); err != nil {
+		return s
+	}
+	// An empty field is the model saying nothing, so hand back nothing. Returning
+	// the raw object here would write `{"summary":""}` into his notes.
+	return strings.TrimSpace(parsed.Summary)
 }
 
 // captureWiring — the recorder plus what it needs to write the result down.