feat(ios): add long-press menus for links

[hryhoriiK97]

What/Why?

Adds linkContextMenuItems: a native menu when a link is long-pressed, on iOS 17 and later. Proposed in #864.

This replaces #865. The feature and its native approach are @juliusmarminge's; here it is reworked to fit the link API the pill work established and stacked on feat/link-pill-icon-tint (#921), so the diff shows only the menus.

What changed compared with #865:

• Keyed by URL pattern, not by exact URL. Keys are regex patterns matched like markdownStyle.linkVariants, so one entry covers every link of a kind and the app does not have to list each link of each message.
• The value is the list of items, and the prop is named linkContextMenuItems, next to contextMenuItems. The menu is titled with the link's text, or its pill label, so no title has to be configured.
• Native is told only when the menus change. feat: add per-link native context menus on iOS #865 rebuilt every menu on each prop update, including every streaming update.
• Table menus lift only the link, not the whole table.
• A pill is lifted as itself. UIKit lifts a pressed text item on a padded box tinted from the pill's colors, which hides the pill's look. A pill with a menu is lifted as an image of itself instead, in text and in tables alike. Plain links keep the system highlight.

API

<EnrichedMarkdownText
  markdown="Open [README.md](https://example.com/files/README.md) or ask [@gregory](user:gregory)."
  linkContextMenuItems={{
    '^https://example\\.com/files/': [
      { text: 'Copy path', icon: 'doc.on.doc', onPress: ({ url }) => copyPath(url) },
      { text: 'Delete', icon: 'trash', destructive: true, onPress: ({ url }) => deleteFile(url) },
    ],
    '^user:': [{ text: 'Mention', icon: 'at', onPress: ({ url }) => mention(url) }],
  }}
  onLinkLongPress={({ url }) => showFallbackMenu(url)}
/>

• The longest pattern that matches a link's URL supplies its menu. A pattern anchored to one URL gives that link its own menu.
• A link with a menu shows it instead of onLinkLongPress and the system link preview. A link that matches no pattern, or whose pattern has no visible items, keeps its existing long-press behavior.
• Items have text, onPress({ url }) and optional icon (SF Symbol), visible, disabled, destructive. text identifies the item within its pattern.
• Android, macOS and iOS below 17 ignore the prop; onLinkLongPress is the hook there.

Implementation

• JS: normalizeLinkPatternEntries is the ordering rule linkVariants already used (longest pattern first, invalid regexes dropped), now shared by both props. The menus are flattened without callbacks and compared structurally, so a re-render that only changes callbacks sends nothing to native. Native reports a press with the URL and the pattern that supplied the menu, and JS looks the item up in the current value; a press on an item that is no longer offered is ignored.
• iOS: ENRMLinkContextMenus holds typed entries, compiles each pattern once and remembers which entry a URL matched. One function, ENRMLinkMenuConfigurationForTextItem, answers the iOS 17 text-item menu callback for the three text view delegates (both components and the blockquote container). The table grid reports the link under a point with its title and frame, which the table container uses for a targeted preview.
• iOS, lifting a pill: ENRMMarkdownTextView presents the menu of a pill itself, through its own UIContextMenuInteraction, and reads the menus from its delegate (ENRMLinkContextMenuSource). The text-item callback gives UIKit no menu for such a pill; with one, UIKit builds its own box around the pill before ours lifts. ENRMLinkMenuLift, shared with the table, lays an image of the link over its view for UIKit to lift: a preview is drawn only from a view that is on screen, and UIKit hides that view while the menu is open, so lifting through a visible path hid the whole table. The pill in the text draws nothing while its copy is lifted, and new text takes the copy down.
• iOS, tables: the table's own menu and a link's menu are told apart by the stored link frame. UIKit replaces a nil configuration identifier with one of its own, so the earlier identifier check sent the table's menu down the link path.
• Android: the prop is accepted and ignored.
• linkContextMenuItems is added to the web list of native-only props.

One thing to know when reviewing: implementing the iOS 17 text-item menu callback also puts links without a menu on that path. They behave as before: the system menu with its preview, or onLinkLongPress when previews are off. Both cases were checked on a device.

Testing

CI does not run on this PR, because the workflow only triggers for PRs that target main. Run locally on this head:

• Jest: 76 pass, including the tests from feat: add per-link native context menus on iOS #865 updated to the new shape (flattening, pattern order, change detection, dispatch guards, stale presses after an update).
• Android: builds, Kotlin lint clean.
• iOS: builds. No native tests were added for the menus.
• On an iOS simulator (iPhone 17, iOS 26.5), with a local demo screen that is not part of this PR:
  • a pill, a pill with a per-link label, and a plain two-line link each show the menu, titled with what the link shows;
  • an item press reaches JS with the link's URL; a disabled item is greyed out, a destructive one is red;
  • a pill inside a blockquote and a pill inside a table show the menu, and in the table only the pill is lifted;
  • long-pressing a table outside a link still lifts the whole table with its own menu, also right after a link menu;
  • a link with no menu fires onLinkLongPress exactly once per long press.
  • a link with no menu and no onLinkLongPress still shows the system link preview and menu.

The pill lift (the last two commits) was checked by hand by @hryhoriiK97 on iOS 26 simulators, on a dark local demo screen: pills in a paragraph, a list, a blockquote and a table lift as themselves with no box before the menu; long-pressing plain text still starts a selection; a plain link with a menu still shows it.

Not covered: iOS below 17, iOS 17 and 18 for the pill lift, VoiceOver, the pill lift in light appearance, and the Storybook story on a device. On macOS the files compiled before the last two commits (that build fails for two errors that already exist on the base branch); it was not rebuilt after them, and their new code is iOS-only behind TARGET_OS_OSX guards. The Maestro flow from #865 is not included: it was written for the old shape and had not been run.

PR Checklist

• Code compiles and runs on iOS
• Code compiles and runs on Android
• Updated documentation/README if applicable
• Ran example app to verify changes
• E2E tests are passing
• Required E2E tests have been added (if applicable)

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