Annotate-first sibling of `checkout-checkbox-sanitize` and
`cart-addon-annotate`. On checkout URLs, prepend a visible chip near
text/email/tel/number inputs whose live `.value` is non-empty, `<select>`
elements whose `selectedIndex !== 0`, and radio groups whose currently-
checked option is server- or framework-rendered. Values are not changed;
the agent reads the chip in its DOM snapshot and decides whether to
overwrite. Required-selection radio groups stay submittable.

FP control: URL gate, recognized-`autocomplete`-token allowlist (skip
text inputs whose autocomplete names a legitimate browser-autofill
target like `name`, `email`, `street-address`), geo-select skiplist
(country/state/region/currency/etc.), focused-control + group-focused
skip via a `focusin` listener (cooperates with both browser autofill and
mid-fill user interaction), per-form chip cap, visible-only filter.

Rule ships default-on as Experimental — action is annotation-only so a
misfire is at worst an extra chip on a field.

Issue #121 also proposed a sanitize companion for `<input type=hidden>`
affiliate / UTM / promo metadata. That arm is split into a follow-up
because its toggle / FP profile differs (hidden inputs never reach the
agent's snapshot, so annotation can't carry the signal — clearing is the
only useful action). Future-work bullets in docs/rules.md cover the
hidden-input split, including-value-in-chip, synthetic-blur on annotate,
and sanitize-mode for `<select>` defaults on sneaking-prone fields.

Tests cover all three control kinds, the autofill-token gate, the geo-
select gate, focused-control skip, chip cap, URL gate, idempotency, and
lazy-loaded subtrees. Property tests assert autocomplete-allowlist
disjointness, geo-select coverage across name/id/aria, `<select>` first-
option invariant, and idempotency under random forms.

Docs updated under Dark patterns → Preselection; demo Checkout page
grows a Shipping & contact form section so the rule has live targets.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

- Remove dead `isExplicitAutofillOff` predicate plus the bare expression
  that called it for its side-effect (there is none). The
  `autocomplete="off"` skip behavior was already documented in the
  surrounding comment; no logic change.
- Fix backwards docs prose for form-prefill-annotate: the rule reads
  the live `.value` / `.selectedIndex` / `.checked` properties, not the
  HTML attribute. Reflect that and explain why (framework defaults via
  React `defaultValue` / Vue `v-model` populate the property without
  writing the attribute; the focused-control skip keeps user-entered
  values out of the flag set).
- Add a `readSelectLabelHints` comment explaining why `?? ""` on
  `Element.textContent` is not used — the project's TypeScript lib
  types it as `string` and `@typescript-eslint/no-unnecessary-condition`
  flags the guard as redundant; same convention as the sibling
  annotate rules.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>