M18 — Per-rule toggles for the wand

[julia-shtal]

Context. rules.ts already carries // TODO(post-v1): per-rule toggles.

Scope

1. settingsStore / userData/settings.json: add
   wandRuleToggles: Record<ruleId, boolean>, defaulting every existing rule
   id (including M17's new quote rule) to true if the field is absent —
   this must be backward-compatible with settings files written before this
   task existed.
2. Settings view: new subsection listing each rule by its existing name
   field with a checkbox.
3. The wand's invocation path filters rules by the enabled ids before
   folding — runRules/the wand transaction builder should only see enabled
   rules.
4. Confirm with Julia: does adding this optional field require bumping
   SETTINGS_SCHEMA_VERSION per the project's schema-versioning convention
   (../src/shared/schema.ts), or is an additive/backward-compatible field
   exempt? Don't guess — ask before shipping.

Acceptance criteria

• Disabling a rule and running the wand skips exactly that rule; all
  others still apply.
• Fresh install / pre-existing settings file with no wandRuleToggles
  field behaves identically to current (all-rules-on) behavior.
• Toggles persist across restart like every other setting.