fix(dictionary): add full email/URL token to personal dictionary

[leinss]

Summary

The "Add to dictionary" toolbar key (and its long-press-Enter action) added the whole token only when text was selected. With no selection it fell back to getWordRangeAtCursor, which splits on . and @ (word separators) unless URL detection is enabled — and URL detection is off by default. So tapping the key after typing an email address added only the trailing fragment (e.g. xyz of newsletter@leinss.xyz), never the full address, and there was no obvious way to add the address without first manually selecting it.

Changes

• StringUtils: add pure, unit-tested getWhitespaceDelimitedTokenAtCursor() — returns the whitespace-delimited token straddling the cursor, trimming only outer word separators while keeping interior . / @ / _ so a full email or URL is preserved.
• RichInputConnection: add getWhitespaceDelimitedTokenAtCursor() that fetches the surrounding text and delegates to the pure helper.
• InputLogic: the no-selection add-to-dictionary path now uses it instead of getWordRangeAtCursor (drops the now-unused script argument).
• Tests: cover email at end / mid-token / followed by text, trailing-punctuation and bracket trimming, URL, plain word, whitespace-only, and empty input.

Why this is the minimal fix

Capture reads committed text via the InputConnection, so it is independent of composing state and input type. It works in a native email field, a web email field, and a generic web text field (where only the fragment composes). No change to the suggestion engine or tokenizer, and automatic learning stays gated per field type — only this explicit user action writes to the system user dictionary.

Test plan

• make check — unit tests + lint: 350 tests, 0 failures, 7 skipped; lint clean (0 non-baseline errors)
• Emulator E2E (Pixel 6 API 34):
  • Native email field (Contacts editor, textEmailAddress): typed newsletter@leinss.xyz, tapped Add-to-dictionary → toast Added "newsletter@leinss.xyz" to dictionary (full address)
  • Fresh generic field: typed prefix newsl → full address suggested → tapped suggestion → full address inserted
  • Browser <input type="email">: whole token composes; add works
  • Browser <input type="text"> (only the xyz fragment composes — the reported case): Add-to-dictionary still added the full newsletter@leinss.xyz