Release v0.4 + v0.5 to main (spec, conformance, docs)

[shahadulhaider]

Summary

Merges all v0.4 + v0.5 spec, conformance test, and documentation work from the v0.4 development branch into main. The release work shipped to npm/PyPI/Go on 2026-03-15, but the spec repo's main branch was never updated — this PR fixes that drift.

What's Included

v0.4 features:

• Destructuring (object + array) in let bindings and arrow params
• Regex literals (/pattern/flags) with .test(), .match(), .replace()

v0.5 features:

• Math functions (sqrt, log, pow, random, sign, trunc) + constants (PI, E)
• Type predicates (isNumber, isString, isArray, isNull, isObject, isRegex)
• 13 new array methods (sortBy, take, drop, count, sum, avg, compact, partition, keyBy, min, max, first, last)
• fromEntries(), str.split(/regex/) overload, rest parameters in arrows

Spec fixes:

• Node-count and conformance-count contradictions in Architecture section
• Stale "Future" entries for already-shipped features
• v0.4.0 → v0.5.0 in Deliverables table
• Broken #future-v02 anchor

Test suites added (8 files, +1475 lines):

• conformance/collections_v5.yaml (~45 tests)
• conformance/math_v5.yaml (~30 tests)
• conformance/type_predicates.yaml (~22 tests)
• conformance/features_v5.yaml (~20 tests)
• conformance/destructuring.yaml
• conformance/regex_literals.yaml
• Plus README.md and XPR-SPEC.md updates

Conformance Status

All 3 runtimes pass these conformance suites at v0.5.0:

• xpr-js 0.5.0 (npm: @xpr-lang/xpr)
• xpr-python 0.5.0 (PyPI: xpr-lang)
• xpr-go v0.5.0 (Go module proxy)

Merge Strategy

main is a strict ancestor of v0.4 — fast-forward merge is safe.

Commits (9)

496f8e9 docs: link to live docs site
b68e09c docs: update conformance test list to 22 files for v0.5
9b72075 docs: fix spec contradictions for v0.5
2ea42e5 test: fix error substring matches in v0.5 conformance tests
1d43896 spec: add v0.5 features (math, type predicates, collections, rest params)
87ea0b3 test: add v0.5 conformance tests (~110 cases)
4c3f605 test: fix regex ternary test to use string() for comparison
3d0f77c test: add conformance tests for destructuring and regex literals
8880668 spec: add destructuring and regex literal grammar and semantics for v0.4