feat(highlight): preset overhaul, categories, stats, theme colours, per-host profiles

Rules & engine:
- 22 presets (was 11): split status into okstate/warnstate/badstate, add delop,
  createop, danger, secret, level, exitcode, percent, http; status words are
  case-insensitive and cover the ✓ ✔ ✅ ✗ ✘ ✖ ❌ ⚠ symbol set
- value bands: the first number in a match picks the colour
  (percent: <20% red / 20-50% yellow / 50-80% light green / >=80% green)
- optional per-rule `caseInsensitive`, `category`, `bands`; load-time
  `refreshBuiltinRules` upgrades untouched built-in patterns in place

Settings page:
- three-way master switch `highlightMode` (all / basic / off); `basic` runs only
  the five safety+status rules and `off` empties the rule set rather than
  bypassing HighlightStream (which would drop the held tail)
- category column + grouping (`highlightGroupByCategory`), per-rule hit/duration
  stats (`highlightStats`, opt-in sink, snapshot once a second), theme-following
  colours (`highlightThemeColors`, hue-bucket mapping onto the ANSI palette),
  import/export JSON envelope, live preview through the real engine
- named rule subsets bound per host (`highlightPerHost` + `highlightProfiles`
  + `SshConnection.highlightProfileId`); empty ruleIds = every rule

Tests: new tests/hl-rules.mjs (word boundaries, case flag, negative words,
bands, import/export, preview, basic mode, categories, stats, theme colours,
profiles) + profile round-trip in tests/settings-store.mjs

tests/hl-split-smoke.mjs

@@ -3,13 +3,9 @@
 // deliberately nasty chunk splits, and requires byte-identical output vs the
 // single-chunk reference.
 import { compileRules, applyHighlights, HighlightStream } from '../src/renderer/src/terminal/highlightEngine.ts'
+import { DEFAULT_HIGHLIGHT_RULES } from '../src/shared/settings.ts'
 
-const rules = compileRules([
-  { id: 'okstate', pattern: '\\b(SUCCESS|PASS|OK|DONE)\\b', enabled: true, priority: 5, color: { fg: '#3fb950' } },
-  { id: 'badstate', pattern: '\\b(ERROR|FAILED)\\b', enabled: true, priority: 6, color: { fg: '#f85149' } },
-  { id: 'numbers', pattern: '\\b\\d+(?:\\.\\d+)?(?:%)?\\b', enabled: true, priority: 25, color: { fg: '#f2cc60' } },
-  { id: 'url', pattern: 'https?://[^\\s]+', enabled: true, priority: 30, color: { fg: '#58a6ff' } }
-])
+const rules = compileRules(DEFAULT_HIGHLIGHT_RULES)
 
 // kimi-like: truecolor SGR, OSC title, box drawing, per-line repaints
 const banner =