N2/B1+B4+C4: tempering, the expedition achievement wing, arena seasons

B1 — tempering. `!adventure temper` pushes an owned magic item one rung up
the rarity ladder at the blacksmith, capped at Legendary. Rarity lives on
the registry definition, so an upgraded instance records its progress as a
`temper` step count on its own row (adventure_inventory, magic_item_equipped)
and effective rarity is derived on read. The stored base rarity is never
written back, so an item cannot double-bump across a load/save round-trip.
Effects flow through the existing rarity scalars — no new combat math, and
the Legendary cap means this accelerates reaching the current ceiling rather
than raising it.

Costs mirror the crafting ladder (10k/25k/60k/150k, Foraging 15/20/25/30).
Only the Legendary rung consumes a T5 material; gating the lower rungs on
one would make tempering unreachable until a player already clears T5.

Two plan anchors were wrong: thyraks_core and portal_fragment are not
loot-note strings needing promotion — they are UniqueAlways slate entries
that already materialize as inventory rows on every T5 clear.

B4 — expedition achievement wing: first-clear and all-zones-cleared per tier
(10), a quiet-clear for keeping peak threat under 50, and temper_legendary.
The quiet-clear requires max_threat_seen to be *present*, not merely low:
recordMaxThreat samples only on day rollover and never stores a zero, so an
absent key means no threat history, not low threat. The plan's no-death-T4
achievement is not shipped — no per-expedition death counter exists — and
pet-saved-my-life already ships as combat_pet_save.

C4 — arena seasons. Standings are derived from arena_history.created_at per
calendar quarter rather than wiping arena_stats: same visible reset, but
lifetime totals survive for `!arena stats` and no destructive job can fire
twice. Crowns archive to arena_season_titles rather than player_meta.title,
which already carries the Survivalist milestone. Rollover rides the existing
midnight ticker and self-dedups on the season key, so a bot that was down on
the boundary catches up on its next wake.

internal/plugin/achievements.go

@@ -2,6 +2,7 @@ package plugin
 
 import (
 	"database/sql"
+	"encoding/json"
 	"fmt"
 	"log/slog"
 	"strings"
@@ -1137,9 +1138,160 @@ func (p *AchievementsPlugin) buildAchievements() []achievementDef {
 				return false
 			},
 		},
+
+		// ── Expeditions ──
+		// All passive: they read the expedition rows the extract path already
+		// writes. Tier comes from the zone registry, not a column, so the
+		// checks map zone_id → Tier in Go.
+		{
+			ID: "expedition_clear_t1", Name: "Off the Porch", Description: "Cleared your first Tier 1 zone. It only gets worse from here.",
+			Emoji: "🗺️",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedAnyZoneOfTier(d, u, 1) },
+		},
+		{
+			ID: "expedition_clear_t2", Name: "Reasonably Lost", Description: "Cleared a Tier 2 zone. The map stops being a suggestion.",
+			Emoji: "🗺️",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedAnyZoneOfTier(d, u, 2) },
+		},
+		{
+			ID: "expedition_clear_t3", Name: "Deep Enough", Description: "Cleared a Tier 3 zone. Someone should have stopped you.",
+			Emoji: "🗺️",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedAnyZoneOfTier(d, u, 3) },
+		},
+		{
+			ID: "expedition_clear_t4", Name: "Past the Warnings", Description: "Cleared a Tier 4 zone. The signs were quite clear.",
+			Emoji: "🗺️",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedAnyZoneOfTier(d, u, 4) },
+		},
+		{
+			ID: "expedition_clear_t5", Name: "Where the Map Ends", Description: "Cleared a Tier 5 zone. There was nothing left to be brave about.",
+			Emoji: "🗺️",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedAnyZoneOfTier(d, u, 5) },
+		},
+		{
+			ID: "expedition_master_t1", Name: "Warren Cartography", Description: "Cleared every Tier 1 zone. Thorough.",
+			Emoji: "🧭",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedEveryZoneOfTier(d, u, 1) },
+		},
+		{
+			ID: "expedition_master_t2", Name: "No Stone Unturned", Description: "Cleared every Tier 2 zone.",
+			Emoji: "🧭",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedEveryZoneOfTier(d, u, 2) },
+		},
+		{
+			ID: "expedition_master_t3", Name: "Completionist's Limp", Description: "Cleared every Tier 3 zone. Walk it off.",
+			Emoji: "🧭",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedEveryZoneOfTier(d, u, 3) },
+		},
+		{
+			ID: "expedition_master_t4", Name: "Nowhere Left to Go Wrong", Description: "Cleared every Tier 4 zone.",
+			Emoji: "🧭",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedEveryZoneOfTier(d, u, 4) },
+		},
+		{
+			ID: "expedition_master_t5", Name: "The Long Way Down", Description: "Cleared every Tier 5 zone. Both of them. All the way.",
+			Emoji: "🧭",
+			Check: func(d *sql.DB, u id.UserID) bool { return clearedEveryZoneOfTier(d, u, 5) },
+		},
+		{
+			ID: "expedition_quiet_clear", Name: "Nobody Saw Anything", Description: "Cleared a zone without threat ever passing 50. You were never here.",
+			Emoji: "🌑",
+			Check: clearedUnderThreat50,
+		},
+		{
+			ID: "temper_legendary", Name: "Hot Enough", Description: "Tempered an item all the way to Legendary. The blacksmith needed a moment.",
+			Emoji: "🔨",
+			Check: func(d *sql.DB, u id.UserID) bool {
+				// Granted by the temper path on reaching Legendary
+				return false
+			},
+		},
 	}
 }
 
+// ── Expedition achievement helpers ──────────────────────────────────────────
+
+// clearedZoneIDs returns the zones this player has beaten outright. Boss-
+// defeated gates out extractions that merely ended in 'complete'.
+func clearedZoneIDs(d *sql.DB, userID id.UserID) map[ZoneID]bool {
+	out := map[ZoneID]bool{}
+	rows, err := d.Query(
+		`SELECT DISTINCT zone_id FROM dnd_expedition
+		 WHERE user_id = ? AND status = ? AND boss_defeated = 1`,
+		string(userID), ExpeditionStatusComplete)
+	if err != nil {
+		return out
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var z string
+		if err := rows.Scan(&z); err != nil {
+			return out
+		}
+		out[ZoneID(z)] = true
+	}
+	return out
+}
+
+func clearedAnyZoneOfTier(d *sql.DB, userID id.UserID, tier ZoneTier) bool {
+	cleared := clearedZoneIDs(d, userID)
+	for zid := range cleared {
+		if z, ok := getZone(zid); ok && z.Tier == tier {
+			return true
+		}
+	}
+	return false
+}
+
+func clearedEveryZoneOfTier(d *sql.DB, userID id.UserID, tier ZoneTier) bool {
+	cleared := clearedZoneIDs(d, userID)
+	seen := 0
+	for _, z := range allZones() {
+		if z.Tier != tier {
+			continue
+		}
+		if !cleared[z.ID] {
+			return false
+		}
+		seen++
+	}
+	return seen > 0
+}
+
+// clearedUnderThreat50 looks for a cleared expedition whose peak threat never
+// crossed 50 — the same max_threat_seen sample the Patient Zero milestone
+// reads, so the two reward the same play.
+//
+// The key's *presence* is required, not just a low value. recordMaxThreat only
+// samples on day rollover and never stores a zero, so an absent key means the
+// expedition has no threat history at all (a same-day clear) — which is not
+// evidence that threat stayed low.
+func clearedUnderThreat50(d *sql.DB, userID id.UserID) bool {
+	rows, err := d.Query(
+		`SELECT region_state FROM dnd_expedition
+		 WHERE user_id = ? AND status = ? AND boss_defeated = 1`,
+		string(userID), ExpeditionStatusComplete)
+	if err != nil {
+		return false
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var raw string
+		if err := rows.Scan(&raw); err != nil {
+			return false
+		}
+		var state map[string]any
+		if json.Unmarshal([]byte(raw), &state) != nil {
+			continue
+		}
+		peak, ok := state[regionStateMaxThreatKey].(float64)
+		if ok && int(peak) < 50 {
+			return true
+		}
+	}
+	return false
+}
+
 // statGTE checks if a user_stats column is >= threshold.
 var allowedStatColumns = map[string]bool{
 	"total_messages":     true,