feat(intl): implement Intl.Segmenter (grapheme/word/sentence) — closes #4877

[proggeramlug]

Summary

Implements Intl.Segmenter, the last ANSI-width dependency wall before ink (#348). string-width@7+ / wrap-ansi@9+ call new Intl.Segmenter() at module top-level, so before this, merely importing them (and therefore ink) threw TypeError: is not a constructor.

Closes #4877.

What changed

crates/perry-runtime/src/intl.rs — adds a Segmenter constructor alongside the existing NumberFormat / DateTimeFormat / Collator, reusing their bound-thunk + prototype pattern:

• new Intl.Segmenter(locales?, { granularity }) — defaults to grapheme; an invalid granularity throws the spec RangeError.
• .segment(str) returns a JS array of { segment, index, input, isWordLike? } records — iterable / spreadable, covering both [...seg.segment(s)] and for (const {segment} of seg.segment(s)) (the shapes string-width / wrap-ansi actually use). index is the UTF-16 code-unit offset per spec; isWordLike is emitted only for word granularity.
• .resolvedOptions() → { locale, granularity }.

Backed by the pure-Rust unicode-segmentation crate (UAX #29 — extended grapheme clusters incl. emoji ZWJ sequences / combining marks / regional-indicator flags, word, and sentence boundaries). It was already in our lock graph via convert_case; promoted to a direct perry-runtime dependency.

No codegen allowlist change was needed: new Intl.Segmenter() is a member-expression construct that resolves through the runtime Intl namespace, exactly like the existing new Intl.NumberFormat().

Verification (Perry vs node)

Byte-for-byte match against Node on:

• The issue's exact repro: typeof Intl.Segmenter → function; [...s.segment('a👨‍👩‍👧b')].map(x => x.segment) → [ 'a', '👨‍👩‍👧', 'b' ]
• word granularity with isWordLike, sentence granularity, resolvedOptions()
• UTF-16 index on astral chars (😀 → next index 2)
• The RangeError message for an invalid granularity
• The for-of destructuring form
• Existing NumberFormat / DateTimeFormat / Collator output unchanged; Segmenter.name and .prototype.segment.length correct.

cargo fmt --check clean.

Notes

• Per maintainer convention, version bump + CHANGELOG entry are left for merge time.
• This clears the string-width / wrap-ansi module-init wall; ink's next documented gate is the yoga-layout WASM runtime.

Related

• Compile ink (React-based TUI framework) end-to-end via perry.compilePackages #348 (ink end-to-end), Codegen: new MessageChannel() global constructor unlinked/non-constructible — routes to stdlib symbol, breaks React scheduler init #4873 / fix(hir): global new MessageChannel() routes to always-linked runtime constructor (#4873) #4875 (previous MessageChannel wall)