fix(desktop): render text reaction fallbacks safely

[AaronGoldsmith]

Summary

• Render no-URL literal kind-7 reactions as bounded text unless the content is exactly one well-formed native emoji grapheme.
• Strip only valid outer shortcode colons for presentation (for example, :missing_reaction: displays as missing_reaction), while preserving raw reaction content for titles, accessibility, and toggle identity.
• Apply the same bounded fallback presentation in hover popovers so unresolved shortcodes and long arbitrary text cannot overflow the fixed glyph area; the separate reaction name remains raw.
• Keep image custom emoji exclusively driven by the NIP-30 emojiUrl branch.
• Bound and left-align long literal reaction text so it truncates without overlapping its count.

Kind-7 reaction content is literal under NIP-25, so existing or legacy arbitrary-text events retain their meaning and are rendered safely rather than rejected. NIP-30's matching emoji tag / resolved emojiUrl remains the only custom-image signal.

This is intentionally different from:

• fix(relay): stop panic when reacting to a project root or comment #4973, which fixes a relay ingest panic for reactions on channel-less project events.
• fix(desktop): integer-align custom reaction emoji #4779, which fixed custom-image alignment, not no-URL literal fallback rendering.

This PR is Desktop-only: it changes no relay ingest, persistence, protocol, or channel derivation. A possible CLI warning for an unknown :shortcode: sent without --emoji-url is intentionally deferred and not coupled to rendering compatibility.

Reproduction

buzz reactions add --event <event-id> --emoji :missing_reaction:

The resulting kind-7 event has no matching NIP-30 emoji tag, so Desktop must treat the content as a text fallback rather than forcing it into a native-emoji box.

Testing

• pnpm biome check src/features/messages/ui/MessageReactions.tsx src/features/messages/lib/reactionGlyphPresentation.ts src/features/messages/lib/reactionGlyphPresentation.test.mjs src/shared/lib/emojiOnly.ts tests/e2e/reaction-names.spec.ts
• pnpm test (4,373 passed)
• pnpm build:e2e
• pnpm exec playwright test tests/e2e/reaction-names.spec.ts (3 passed), covering:
  • NIP-30 custom-image hover regression
  • unresolved shortcode pill + hover popover
  • arbitrary ship it pill + hover popover
  • long literal pill/count geometry, truncation, and hover overflow bounds
• sq agents review main...HEAD --local ... after addressing its malformed-ZWJ finding (final local review: no findings)

Screenshots from Testing

Pill row: unresolved shortcode, arbitrary text, and long literal text — each bounded, left-aligned, and truncated without overlapping its count

Case	Rendering
Short unresolved shortcode in hover popover — outer colons preserved in the raw reaction name
Max-length literal content in hover popover — wraps within the popover instead of overflowing the glyph area

Original UI rendering bug example

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Document or stop exporting the emoji helpers

This commit turns both isNativeEmojiCluster and readGrapheme into exported APIs without adding doc comments, even though both remain implementation details used only within emojiOnly.ts. Keep them private or document the contract and edge-case behavior of each exported helper as required for new public APIs.

AGENTS.md reference: AGENTS.md:L116-L116

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