Announce tick-inferred routines, opt-in and rate-limited (#247, #43)

The digestion tick already runs the pattern detector over all recorded
events (67563ed) and writes a proposed_routines row. What was missing is
the other half of #247: a proposal that nobody is at the mic for reaches
nothing but the /routines page, so a pattern noticed at 03:00 is only
seen if he goes looking.

This wires the tick's proposals into the existing care-delivery path
rather than a second channel: sev1 nudge, loop.Gate, dispatcher, same
routing table as an accepted routine. Restraints, since a feature that
speaks unprompted is the easiest way to turn Maven into a nag:

  - off unless configured — the new pattern_proposals block, absent by
    default, and deploy/mavend.json ships notify: false;
  - at most one announcement per tick however many patterns surfaced;
  - at most one per cooldown (24h default) across all pairs;
  - sev1, so quiet hours, away and snooze suppress it;
  - suppressed means dropped, not queued — /routines still has it;
  - once per pair for good, since proposed_routines is
    UNIQUE(action, object) and the row survives dismissal.

The body is pattern.PhraseRoutine's literal Russian, not LLM-worded, so
an inferred routine cannot arrive describing something never observed.

Also raises pattern.MinEvents from 3 to 4 — the interval-quality item on
#43. Two intervals with a ±50% band is a coincidence with a mean, not a
pattern, and now that a scan of all history can announce itself the cost
of a false positive is a permanent dismissal of that pair.

internal/config/config.go

@@ -140,6 +140,12 @@ type Config struct {
 	// item. See internal/morning for the evaluation engine. Empty ⇒ disabled.
 	MorningRoutines []MorningRoutineConfig `json:"morning_routines,omitempty"`
 
+	// PatternProposals — whether a routine the digestion tick inferred on its
+	// own may be announced, and how often. nil / absent ⇒ silent detection
+	// only: proposals are written for /routines and never announced. See
+	// PatternProposalConfig.
+	PatternProposals *PatternProposalConfig `json:"pattern_proposals,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
@@ -352,6 +358,40 @@ type DigestConfig struct {
 	SeverityCeiling int      `json:"severity_ceiling,omitempty"` // max sev batched
 }
 
+// PatternProposalConfig — announcement policy for routines the digestion tick
+// inferred by itself (Vikunja #247, #43).
+//
+// Detection is always on and always silent by default: the tick writes a
+// proposed_routines row and the /routines page shows it. Notify is what turns
+// "she noticed" into "she said something", and it is OFF unless configured —
+// Maven is not a nag and not autonomous, so a behaviour that speaks without
+// being asked has to be switched on deliberately, like weather and telegram.
+//
+// When Notify is on, the announcement is still heavily restrained:
+//   - at most one proposal per tick, however many were detected;
+//   - at most one per Cooldown across all pairs (not per pair), so a batch of
+//     freshly-detected patterns cannot turn into a queue of interruptions;
+//   - through the ordinary care-class gate (quiet hours / away / snooze), at
+//     sev1 — the lowest severity there is. A proposal is the least urgent
+//     thing Maven can say.
+//
+// A pair is only ever announced once, because it is only ever proposed once:
+// proposed_routines is UNIQUE(action, object) and the row survives dismissal.
+type PatternProposalConfig struct {
+	// Notify — announce newly inferred routines. Default false.
+	Notify bool `json:"notify,omitempty"`
+
+	// Cooldown — minimum spacing between two proposal announcements. 0 ⇒
+	// DefaultProposalCooldown (24h).
+	Cooldown Duration `json:"cooldown,omitempty"`
+}
+
+// AnnounceProposals reports whether inferred routines may be announced. Safe
+// on a nil receiver — an absent config block means silent detection.
+func (p *PatternProposalConfig) AnnounceProposals() bool {
+	return p != nil && p.Notify
+}
+
 // 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.
@@ -448,6 +488,11 @@ const (
 	DefaultLLMRouter = true
 
 	DefaultFactEnrichmentInterval = 30 * time.Second
+
+	// DefaultProposalCooldown — one inferred-routine announcement per day at
+	// 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
 )
 
 // Load reads the JSON config at path and applies defaults. A missing file is
@@ -520,6 +565,12 @@ func (c *Config) applyDefaults() {
 		c.Digest.SeverityCeiling = 2
 	}
 
+	// Absent block stays nil (⇒ silent detection). Present-but-partial gets the
+	// cooldown default, so `{"notify": true}` is enough to switch it on.
+	if c.PatternProposals != nil && c.PatternProposals.Cooldown <= 0 {
+		c.PatternProposals.Cooldown = Duration(DefaultProposalCooldown)
+	}
+
 	if c.Voice != nil {
 		if c.Voice.RouterThreshold <= 0 {
 			c.Voice.RouterThreshold = DefaultRouterThreshold

internal/pattern/detector.go

@@ -20,9 +20,19 @@ type ProposedRoutine struct {
 const MaxIntervalRatio = 1.5
 
 // MinEvents is the minimum number of events needed to detect a pattern.
-// With N events, there are N-1 intervals; we need at least 2 intervals
-// before proposing anything.
-const MinEvents = 3
+// With N events there are N-1 intervals, so 4 events means 3 intervals.
+//
+// This used to be 3 (two intervals), which is not a pattern — it is a
+// coincidence with a mean. Two gaps of similar length happen constantly:
+// water the plants on a Sunday, again the next Sunday, once more the Sunday
+// after, and a detector with a ±50% band calls that a weekly routine. The
+// cost of being wrong is asymmetric now that the digestion tick scans all of
+// history on its own schedule and can announce what it finds: a false
+// positive is something the owner has to read and dismiss, and a dismissal
+// is permanent, so one bad guess burns that action+object pair forever.
+// Three intervals is the cheapest bar that makes a run distinguishable from
+// a repeat. False negatives cost one more observation and nothing else.
+const MinEvents = 4
 
 // Detect checks whether a sequence of events for the same action+object
 // forms a stable recurring pattern. Returns a ProposedRoutine when:

internal/pattern/detector_test.go

@@ -6,12 +6,13 @@ import (
 )
 
 func TestDetectEnoughEvents(t *testing.T) {
-	// 3 events with 7-day intervals → stable pattern
+	// MinEvents events with 7-day intervals → stable pattern
 	base := time.Date(2026, 7, 1, 12, 0, 0, 0, time.UTC)
 	events := []Event{
 		{Action: "refill", Object: "cat_water", Ts: base},
 		{Action: "refill", Object: "cat_water", Ts: base.Add(7 * 24 * time.Hour)},
 		{Action: "refill", Object: "cat_water", Ts: base.Add(14 * 24 * time.Hour)},
+		{Action: "refill", Object: "cat_water", Ts: base.Add(21 * 24 * time.Hour)},
 	}
 
 	r, err := Detect(events)
@@ -24,8 +25,8 @@ func TestDetectEnoughEvents(t *testing.T) {
 	if r.Action != "refill" || r.Object != "cat_water" {
 		t.Fatalf("action/object: want refill/cat_water, got %s/%s", r.Action, r.Object)
 	}
-	if r.N != 3 {
-		t.Fatalf("want N=3, got %d", r.N)
+	if r.N != 4 {
+		t.Fatalf("want N=4, got %d", r.N)
 	}
 	// ~7 days
 	if r.IntervalDays < 6.9 || r.IntervalDays > 7.1 {
@@ -33,19 +34,28 @@ func TestDetectEnoughEvents(t *testing.T) {
 	}
 }
 
+// TestDetectNotEnoughEvents — two intervals are a coincidence, not a routine
+// (Vikunja #43). Three same-day-of-week events used to be enough to propose a
+// weekly reminder; MinEvents is 4 now so a repeat has to happen a third time
+// before Maven calls it a pattern.
 func TestDetectNotEnoughEvents(t *testing.T) {
 	base := time.Date(2026, 7, 1, 12, 0, 0, 0, time.UTC)
-	events := []Event{
-		{Action: "refill", Object: "cat_water", Ts: base},
-		{Action: "refill", Object: "cat_water", Ts: base.Add(7 * 24 * time.Hour)},
-	}
-
-	r, err := Detect(events)
-	if err != nil {
-		t.Fatalf("Detect: %v", err)
-	}
-	if r != nil {
-		t.Fatal("want nil for <3 events")
+	for _, n := range []int{1, 2, MinEvents - 1} {
+		events := make([]Event, n)
+		for i := range events {
+			events[i] = Event{
+				Action: "refill",
+				Object: "cat_water",
+				Ts:     base.Add(time.Duration(i) * 7 * 24 * time.Hour),
+			}
+		}
+		r, err := Detect(events)
+		if err != nil {
+			t.Fatalf("Detect(%d events): %v", n, err)
+		}
+		if r != nil {
+			t.Fatalf("Detect(%d events) proposed %+v, want nil below MinEvents=%d", n, r, MinEvents)
+		}
 	}
 }
 
@@ -68,12 +78,13 @@ func TestDetectEmpty(t *testing.T) {
 }
 
 func TestDetectIrregularRejects(t *testing.T) {
-	// 3 events but wildly irregular: 1 day, then 14 days → ratio 14 > 1.5
+	// wildly irregular: 1 day, then 14 days → ratio 14 > 1.5
 	base := time.Date(2026, 7, 1, 12, 0, 0, 0, time.UTC)
 	events := []Event{
 		{Action: "refill", Object: "cat_water", Ts: base},
 		{Action: "refill", Object: "cat_water", Ts: base.Add(1 * 24 * time.Hour)},
 		{Action: "refill", Object: "cat_water", Ts: base.Add(15 * 24 * time.Hour)},
+		{Action: "refill", Object: "cat_water", Ts: base.Add(16 * 24 * time.Hour)},
 	}
 
 	r, err := Detect(events)
@@ -117,6 +128,7 @@ func TestDetectSameTimestamp(t *testing.T) {
 		{Action: "refill", Object: "cat_water", Ts: base},
 		{Action: "refill", Object: "cat_water", Ts: base},
 		{Action: "refill", Object: "cat_water", Ts: base.Add(7 * 24 * time.Hour)},
+		{Action: "refill", Object: "cat_water", Ts: base.Add(14 * 24 * time.Hour)},
 	}
 
 	r, err := Detect(events)