Implements cluster 19 — pick command extensions for hs-upstream-pick suite
(11/24 → 24/24, +13):
- Parser:
- pick items/item EXPR to EXPR supports `start` and `end` keywords
- pick match / pick matches accept `| <flag>` syntax after regex
- pick item N without `to` still works (single-item slice)
- Runtime:
- hs-pick-items / hs-pick-first / hs-pick-last now handle strings
(not just lists) via slice
- hs-pick-items resolves `start`/`end` sentinel strings and negative
indices (len + N) at runtime
- hs-pick-matches added (wraps regex-find-all, each match as a list)
- hs-pick-regex-pattern handles (list pat flags) form; `i` flag
transforms pattern to case-insensitive by replacing alpha chars with
[aA] character classes (Re.Pcre has no inline-flag support)
- Generator:
- extract_hs_expr now decodes JS string escape sequences (\" -> ",
\\ -> \) instead of stripping all backslashes, then re-escapes for
SX. Preserves regex escapes (\d, \s), CSS escapes, and lambda `\`
syntax for String.raw template literals while still producing
correct output for regular JS strings.
Smoke (0-195): 170/195 unchanged (no regressions).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
giles
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