feat(sub): leastLoad member weights for subscription balancers (#6304)

* feat(model): add MemberWeights to SubBalancer

Per-inbound leastLoad weights, stored with the same gorm json serializer
as InboundIds so AutoMigrate adds the text column on every dialect
(postgresModelSettled sees the missing column and re-runs). Absent
entries mean weight 1.0; only meaningful for strategy leastLoad.

* feat(sub): accept memberWeights on the sub-balancer API

Parsed as one JSON form field (gin cannot bind bracket-keyed maps from
urlencoded bodies). validate() rejects weights under any strategy but
leastLoad — xray would silently ignore costs there, so storing them
would pretend a knob exists. Non-positive weights error instead of
defaulting: a zero usually means a typo'd "never pick this node".
Entries for inbounds no longer selected are dropped on save.

* feat(sub): emit leastLoad strategy costs from member weights

costs[] is built after the tagging loop reuses the exact retagged tags
(bal-N-protocol[-k]) and each member's owning inbound id. Members
without a configured weight default to 1.0, but costs are omitted
entirely unless at least one explicit weight survives — an all-1.0
array would bloat every subscription response for no effect.

* feat(sub-balancers): leastLoad member weight inputs

Weight fields render only under leastLoad and hide on strategy change
without dropping their values, so an accidental toggle away and back
loses nothing until save; non-leastLoad submits strip them entirely
because xray would ignore costs. Weights travel as one JSON form field
(gin cannot bind bracket-keyed maps) and every locale gets the three
new keys in the same commit per the dead-keys rule.

* docs(api): document memberWeights on sub-balancers

leastLoad-only JSON form field; update notes that omitting it clears
stored weights. Regenerated openapi artifacts via make gen + the docs
copy/gen:api step nothing checks automatically.

* fix(api-docs): use the allowed object ParamType for memberWeights

* fix(sub-balancers): cap the member-weight list height

Many selected inbounds pushed the modal body past the viewport. The
weight rows now scroll inside a 220px viewport, mirroring the inbound
picker's listHeight so both lists read the same.

* fix(sub): anchor leastLoad cost matches to exact member tags

Verified against xray-core: without regexp, WeightManager matches costs
by substring (strings.Index), so the bare tag "bal-1-vless" also hits
the deduplicated "bal-1-vless-2" and both members get the first
entry's weight. Anchored ^tag$ regexps make every cost entry match only
its own member. Also confirmed value<=0 makes xray derive a weight from
the first digit of the matched tag — validating weights > 0 server-side
was the right call.

* fix(sub-balancers): keep member weights across the enabled toggle

The table's toggleEnabled re-posted a full-row payload without
memberWeights, and the update path treats an absent key as "erase" —
flipping the switch silently dropped every configured weight. Round-trip
the stored weights through the toggle payload, and prove persistence
with a re-Get in the weight-validation test (the returned struct alone
would stay green even if Save skipped the column).

* fix(sub-balancers): address review on member weights

- omitempty on MemberWeights: the panel sends null for every pre-existing
  and non-leastLoad balancer, which failed the hand-written zod response
  schema on every fetch (zod .optional() accepts undefined only; switched
  to .nullish() per repo convention) and drifted the generated contract.
  Regenerated openapi artifacts + docs copy + MDX.
- Bound weights to the positive float32 range: xray decodes costs as
  float32, so an over-range value makes clients reject the whole
  subscription document and an underflow decays to the tag-digit
  fallback weight. Tests for both directions.
- Trim six comment blocks to the 2-line cap from CLAUDE.md.

---------

Co-authored-by: DIMFLIX <dimflix@users.noreply.github.com>

internal/sub/sub_balancer_test.go

@@ -420,3 +420,91 @@ func observatoryPingConfig(t *testing.T, docs []map[string]any, remarks string)
 	ping, _ := obs["pingConfig"].(map[string]any)
 	return ping
 }
+
+func balancerStrategy(t *testing.T, docs []map[string]any, remarks string) map[string]any {
+	t.Helper()
+	doc := findDocByRemarks(docs, remarks)
+	if doc == nil {
+		t.Fatalf("balancer doc %q missing", remarks)
+	}
+	routing, _ := doc["routing"].(map[string]any)
+	balancers, _ := routing["balancers"].([]any)
+	strategy, _ := balancers[0].(map[string]any)["strategy"].(map[string]any)
+	return strategy
+}
+
+// leastLoad with configured weights must emit strategy.settings.costs keyed by
+// the retagged member tags; members without a weight count as 1.0.
+func TestSubJson_BalancerLeastLoadCosts(t *testing.T) {
+	seedSubDB(t)
+	fast := seedSubInbound(t, "s1", "fast", 4791, 1, wsTLSStream)
+	slow := seedSubInbound(t, "s1", "slow", 4792, 2, wsTLSStream)
+	seedSubBalancer(t, &model.SubBalancer{
+		Remark: "weighted", Strategy: "leastLoad", InboundIds: []int{fast.Id, slow.Id},
+		MemberWeights: map[int]float64{fast.Id: 0.2}, SortOrder: 1, Enabled: true,
+	})
+
+	js := NewSubJsonService("", "", "", NewSubService(""))
+	out, _, err := js.GetJson("s1", "req.example.com", true)
+	if err != nil {
+		t.Fatalf("GetJson: %v", err)
+	}
+	strategy := balancerStrategy(t, parseSubJsonDocs(t, out), "weighted")
+	settings, _ := strategy["settings"].(map[string]any)
+	costs, _ := settings["costs"].([]any)
+	if len(costs) != 2 {
+		t.Fatalf("costs = %v, want 2 entries:\n%s", costs, out)
+	}
+	first, _ := costs[0].(map[string]any)
+	second, _ := costs[1].(map[string]any)
+	// Anchored regexp is required: xray's plain cost match is substring-based,
+	// so a bare "bal-1-vless" would also hit the deduplicated "bal-1-vless-2".
+	if first["regexp"] != true || first["match"] != "^bal-1-vless$" || first["value"] != 0.2 {
+		t.Fatalf("costs[0] = %v, want regexp ^bal-1-vless$ value=0.2", first)
+	}
+	if second["regexp"] != true || second["match"] != "^bal-1-vless-2$" || second["value"] != 1.0 {
+		t.Fatalf("costs[1] = %v, want regexp ^bal-1-vless-2$ value=1 (default)", second)
+	}
+}
+
+// leastLoad without any configured weight emits no settings at all.
+func TestSubJson_BalancerLeastLoadWithoutWeightsOmitsCosts(t *testing.T) {
+	seedSubDB(t)
+	a := seedSubInbound(t, "s1", "a", 4801, 1, wsTLSStream)
+	b := seedSubInbound(t, "s1", "b", 4802, 2, wsTLSStream)
+	seedSubBalancer(t, &model.SubBalancer{
+		Remark: "plain", Strategy: "leastLoad", InboundIds: []int{a.Id, b.Id}, SortOrder: 1, Enabled: true,
+	})
+
+	js := NewSubJsonService("", "", "", NewSubService(""))
+	out, _, err := js.GetJson("s1", "req.example.com", true)
+	if err != nil {
+		t.Fatalf("GetJson: %v", err)
+	}
+	strategy := balancerStrategy(t, parseSubJsonDocs(t, out), "plain")
+	if _, has := strategy["settings"]; has {
+		t.Fatalf("leastLoad without weights must not emit strategy.settings: %v", strategy["settings"])
+	}
+}
+
+// Emission-side guard independent of validate(): a non-leastLoad row written
+// directly to the DB must still emit no costs — xray would ignore them.
+func TestSubJson_BalancerCostsSkippedForNonLeastLoadStrategy(t *testing.T) {
+	seedSubDB(t)
+	a := seedSubInbound(t, "s1", "a", 4811, 1, wsTLSStream)
+	b := seedSubInbound(t, "s1", "b", 4812, 2, wsTLSStream)
+	seedSubBalancer(t, &model.SubBalancer{
+		Remark: "misconfig", Strategy: "random", InboundIds: []int{a.Id, b.Id},
+		MemberWeights: map[int]float64{a.Id: 0.5}, SortOrder: 1, Enabled: true,
+	})
+
+	js := NewSubJsonService("", "", "", NewSubService(""))
+	out, _, err := js.GetJson("s1", "req.example.com", true)
+	if err != nil {
+		t.Fatalf("GetJson: %v", err)
+	}
+	strategy := balancerStrategy(t, parseSubJsonDocs(t, out), "misconfig")
+	if _, has := strategy["settings"]; has {
+		t.Fatalf("random balancer must never emit costs despite stored weights: %v", strategy)
+	}
+}