Add background memory evaluation, off unless configured (#248)

Ships the real, local, testable part of the memory-evaluation plan
(docs/plans/03-memory-evaluation.md): Maven reads back her own recent
memory on a slow ticker, asks the resident model what it notices, and
records the confident answers as notes.

internal/memeval — not internal/memory/eval.go as the plan says, because
internal/store imports internal/memory for the vector backend and an
evaluator has to read store.Fact/Note/Nudge, which would close the
cycle. Evaluate() gathers RecentFacts/RecentNotes/RecentNudges, prompts
under a GBNF grammar bounded to three {observation, confidence,
suggested_action} objects, drops anything under min_confidence,
deduplicates against what earlier runs wrote, and writes the rest as
notes with source infer:memory-eval. /dash already renders notes with
their source, so the output is visible with no UI change.

cmd/mavend/memoryeval.go drives it on its own goroutine and ticker, not
on the 60s tick: an evaluation is a multi-second round-trip on the same
llama-server that answers voice turns, and it runs hourly at most. The
memory_eval config block is absent by default and absence means the
goroutine does not exist. No llama-server phraser also means no loop —
there is no template fallback, because a "memory evaluation" assembled
from templates is a fixed sentence pretending to be an observation.

What it deliberately cannot do, since this is the feature most likely to
turn Maven into a nag:

  - It cannot speak. No dispatcher reference, no channel, no nudge. An
    observation is a thought she wrote down and he reads on /dash.
    Announcing them is a separate decision with its own opt-in.
  - It cannot act. suggested_action is recorded as text and interpreted
    by nobody — no reminder, routine or fact is created from it.
  - It says nothing about an empty store: no memory means no LLM call,
    so there are no observations invented out of two facts.
  - Its own notes are excluded from the next evaluation's input, and are
    written with a nil embedding so they stay out of the recall pool.

The plan's remaining items (dispatching observations, an /eval IPC
method and trace view, RecentEvents) and the fact that output quality is
entirely unmeasured are written up at the bottom of the plan doc.

internal/config/config.go

@@ -146,6 +146,10 @@ type Config struct {
 	// PatternProposalConfig.
 	PatternProposals *PatternProposalConfig `json:"pattern_proposals,omitempty"`
 
+	// MemoryEval — background memory evaluation (internal/memeval). nil /
+	// absent ⇒ no evaluation loop at all. See MemoryEvalConfig.
+	MemoryEval *MemoryEvalConfig `json:"memory_eval,omitempty"`
+
 	// Praxis — the ecosystem attention-state service. When configured, maven
 	// calls the Praxis HTTP tools API for attention listing and item lifecycle.
 	// Maven never touches Praxis's database directly (ecosystem invariant: no
@@ -392,6 +396,28 @@ func (p *PatternProposalConfig) AnnounceProposals() bool {
 	return p != nil && p.Notify
 }
 
+// MemoryEvalConfig — the background memory-evaluation loop (Vikunja #248).
+// Absent ⇒ off, like every other capability that costs something the owner did
+// not ask for. Each evaluation is a full LLM round-trip on the one resident
+// model, which is the same model answering him; running it hourly by default
+// would put a multi-second stall in front of an occasional voice turn for a
+// feature he may not want.
+//
+// The loop only ever writes notes (source infer:memory-eval, visible on
+// /dash). It cannot speak — see internal/memeval.
+type MemoryEvalConfig struct {
+	// Interval — how often to evaluate. 0 ⇒ DefaultMemoryEvalInterval.
+	Interval Duration `json:"interval,omitempty"`
+
+	// MaxItems — recent facts / notes / nudges fed into one evaluation.
+	// 0 ⇒ memeval.DefaultMaxItems.
+	MaxItems int `json:"max_items,omitempty"`
+
+	// MinConfidence — observations the model scores below this are dropped.
+	// 0 ⇒ memeval.DefaultMinConfidence.
+	MinConfidence float64 `json:"min_confidence,omitempty"`
+}
+
 // PhraserConfig — the LLM-backed phraser seam. The daemon spawns llama-server
 // as a managed subprocess and sends chat-completion requests to phrase nudge
 // and reminder messages. nil ⇒ the template-based Stub is used instead.
@@ -493,6 +519,10 @@ const (
 	// most. A proposal is never urgent; if two patterns surface in the same
 	// hour, the second one waits, and the /routines page has it either way.
 	DefaultProposalCooldown = 24 * time.Hour
+
+	// DefaultMemoryEvalInterval — the plan's cadence (1h) for the memory
+	// evaluation loop, applied only when the block is present at all.
+	DefaultMemoryEvalInterval = time.Hour
 )
 
 // Load reads the JSON config at path and applies defaults. A missing file is
@@ -571,6 +601,12 @@ func (c *Config) applyDefaults() {
 		c.PatternProposals.Cooldown = Duration(DefaultProposalCooldown)
 	}
 
+	// Same rule: absent stays nil (⇒ no evaluation loop), present gets defaults
+	// so `{}` is a valid "on with the plan's cadence".
+	if c.MemoryEval != nil && c.MemoryEval.Interval <= 0 {
+		c.MemoryEval.Interval = Duration(DefaultMemoryEvalInterval)
+	}
+
 	if c.Voice != nil {
 		if c.Voice.RouterThreshold <= 0 {
 			c.Voice.RouterThreshold = DefaultRouterThreshold

internal/config/config_test.go

@@ -243,3 +243,53 @@ func TestDurationRoundTrip(t *testing.T) {
 		t.Errorf("round-trip = %v, want %v", d2, d)
 	}
 }
+
+// Both new opt-in capabilities follow the same rule: absent block ⇒ nil ⇒ the
+// behaviour does not exist. Presence is the enable act, so a bare `{}` block is
+// valid and gets the defaults filled in.
+func TestOptInBlocksAbsentStayNil(t *testing.T) {
+	c, err := Load(writeConfig(t, `{}`))
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if c.PatternProposals != nil {
+		t.Errorf("pattern_proposals absent but got %+v", c.PatternProposals)
+	}
+	if c.PatternProposals.AnnounceProposals() {
+		t.Error("AnnounceProposals() true with no config block")
+	}
+	if c.MemoryEval != nil {
+		t.Errorf("memory_eval absent but got %+v", c.MemoryEval)
+	}
+}
+
+func TestOptInBlocksGetDefaultsWhenPresent(t *testing.T) {
+	c, err := Load(writeConfig(t, `{"pattern_proposals":{"notify":true},"memory_eval":{}}`))
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if !c.PatternProposals.AnnounceProposals() {
+		t.Error("notify:true did not enable announcements")
+	}
+	if time.Duration(c.PatternProposals.Cooldown) != DefaultProposalCooldown {
+		t.Errorf("proposal cooldown = %v, want %v", c.PatternProposals.Cooldown, DefaultProposalCooldown)
+	}
+	if time.Duration(c.MemoryEval.Interval) != DefaultMemoryEvalInterval {
+		t.Errorf("memory eval interval = %v, want %v", c.MemoryEval.Interval, DefaultMemoryEvalInterval)
+	}
+}
+
+// Notify is off even when the block exists — the block is where you tune it,
+// notify:true is the act that lets her speak.
+func TestPatternProposalNotifyDefaultsOff(t *testing.T) {
+	c, err := Load(writeConfig(t, `{"pattern_proposals":{"cooldown":"6h"}}`))
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if c.PatternProposals.AnnounceProposals() {
+		t.Error("notify defaulted to on")
+	}
+	if time.Duration(c.PatternProposals.Cooldown) != 6*time.Hour {
+		t.Errorf("cooldown = %v, want 6h", c.PatternProposals.Cooldown)
+	}
+}