fix: apply pending correctness fixes

Cherry-pick the still-relevant fixes from recent draft PRs without pulling in stale release/docs changes:

- serialize dashboard data loads to avoid concurrent config self-heal writes
- preserve valid per-model default blocks during dashboard model self-heal
- pass structured humanizeError results directly to toast for model import scan failures
- align frontend kernel isLatest with suffix-aware recommended version ordering

Verification:
- node --test tests/*.test.js
- npm run build

tests/humanize-error.test.js

@@ -0,0 +1,17 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+
+import { humanizeError, humanizeErrorText } from '../src/lib/humanize-error.js'
+
+test('humanizeError must not be coerced with String() or template literals', () => {
+  const h = humanizeError(new Error('ECONNREFUSED 127.0.0.1:443'), 'Import scan failed')
+  assert.equal(typeof h, 'object')
+  assert.equal(String(h), '[object Object]')
+  assert.ok(h.message)
+})
+
+test('humanizeErrorText is safe for plain-string contexts', () => {
+  const line = humanizeErrorText(new Error('ENOENT no such file'), 'Import scan failed')
+  assert.match(line, /Import scan failed/)
+  assert.doesNotMatch(line, /\[object Object\]/)
+})

tests/kernel.test.js

@@ -9,8 +9,8 @@
 import test from 'node:test'
 import assert from 'node:assert/strict'
 
-import { parseVersion, versionGte, buildSnapshot } from '../src/lib/kernel.js'
-import { FEATURE_CATALOG, KERNEL_FLOOR } from '../src/lib/feature-catalog.js'
+import { parseVersion, versionGte, buildSnapshot, recommendedIsNewer } from '../src/lib/kernel.js'
+import { FEATURE_CATALOG, KERNEL_FLOOR, KERNEL_TARGET } from '../src/lib/feature-catalog.js'
 
 // ============================================================================
 // parseVersion
@@ -160,14 +160,21 @@ test('buildSnapshot edge case: version slightly below 5.6 feature requirement',
 })
 
 test('buildSnapshot.isLatest works against KERNEL_TARGET', () => {
-  const at_target = buildSnapshot('openclaw', '2026.5.19')
-  const at_chinese_target = buildSnapshot('openclaw', '2026.5.18-zh.1')
-  const above_target = buildSnapshot('openclaw', '2026.6.0')
-  const below_target = buildSnapshot('openclaw', '2026.5.18')
-  assert.equal(at_target.isLatest, true)
-  assert.equal(at_chinese_target.isLatest, true)
-  assert.equal(above_target.isLatest, true)
-  assert.equal(below_target.isLatest, false)
+  const atOfficial = buildSnapshot('openclaw', KERNEL_TARGET.openclaw.official)
+  const atChinese = buildSnapshot('openclaw', KERNEL_TARGET.openclaw.chinese)
+  const aboveTarget = buildSnapshot('openclaw', '2026.6.0')
+  const belowTarget = buildSnapshot('openclaw', '2026.5.18')
+  assert.equal(atOfficial.isLatest, true)
+  assert.equal(atChinese.isLatest, true)
+  assert.equal(aboveTarget.isLatest, true)
+  assert.equal(belowTarget.isLatest, false)
+})
+
+test('recommendedIsNewer matches suffix patch ordering', () => {
+  assert.equal(recommendedIsNewer('2026.5.18-zh.2', '2026.5.18-zh.1'), true)
+  assert.equal(recommendedIsNewer('2026.5.18-zh.1', '2026.5.18-zh.2'), false)
+  assert.equal(recommendedIsNewer('2026.5.18-zh.1', '2026.5.18-zh.1'), false)
+  assert.equal(recommendedIsNewer('2026.5.19', '2026.5.18-zh.9'), true)
 })
 
 // ============================================================================