fix(text): treat authored replace targets as literal text

[rahul05ranjan]

What happens

The replace expression passes the authored to string as the replacement argument of String.prototype.replace/replaceAll (packages/text/src/program.ts). JavaScript treats $&, $$, $`` and $' in a plain replacement string as substitution patterns, so a target like "$& USD"` silently renders as the matched substring:

{ kind: "replace", input: { kind: "literal", value: "price: X" },
  replacements: [{ from: "X", to: "$& USD", mode: "all" }] }

renders price: X USD instead of the authored price: $& USD. $$ collapses to a single $; $ and $' splice in the text before/after the match. The corruption is silent becauseverifyTextTemplate` accepts the expression.

Fix

Pass a replacer function so the authored to is always inserted literally — no other change to the expression's semantics. from was already treated literally, so to now matches it.

Test

Adds a regression test to packages/text/test/text.test.ts pinning authored targets containing $&, $$, $ and $' across bothallandfirstmodes. Focused run of that file: 8 tests pass, including the new one; the new test fails on current main withprice: X $ USDwhereprice: $& $$ USD` is authored.

Fixes #393