feat: speak ~N as "about N"; fix "dedupe" pronunciation

[StuBehan]

Summary

Two things espeak reads wrong in dev output, both fixed in the normalize pipeline.

Changes

• ~N → "about N" — a locale unit/symbol rule so ~ before a number is voiced as an approximation (~1,234 → "about 1234") instead of "tilde one hundred twenty-three". Leaves ~/path and non-numeric ~ untouched.
• "dedupe" pronunciation — glued, espeak reads it as "de-dup" (short u). Added to the dev-term dict as "dee dupe" (reads "dee doop" — confirmed by ear), plus the inflections deduped / deduping / dedupes / dedup. Whole-word, so longer tokens aren't rewritten.

Testing

• New tests/test_text.py cases: tilde before/after a number, ~/path left alone, tilde + decimal end-to-end; dedupe substitution across inflections + case, and a whole-word guard.
• ruff check + ruff format --check clean; mypy clean; pytest — 45 text tests pass.
• Live-checked via stackvox normalize (text) and synthesized the dedupe candidates to pick the spelling by ear.

CHANGELOG.md intentionally untouched — release-please owns it; lands as a feat in the next release.