spb/metrika Public

- fix: script-command verbs were routed AFTER parsing, which rejects
  unknown verbs — .zyq commands could never run; they now route before
  the parser with raw macro arguments
- .zyq scripts: ado-style 'args name…' declaration with backtick macro
  substitution (`0', `k', `name'); scratch-variable scripts verified
  end-to-end against the built-in path
- ZQPluginRegistry: verb-keyed native plugin registry; verbs shadowing
  built-ins rejected at session start; parsed commands validated against
  the declared ZQSyntaxSpec (varlist/if/in/weights/options)
- mutation gating: plugins return a replacement dataset via
  ZQResult.replacementFrame, installed only under 'mutates: true' — a
  non-mutating plugin returning one is an error and the dataset is
  untouched (ZQContext is now a plain value, no writable back-channel)
- ZScorePlugin ships as the reference native plugin, registered by the
  app ('zscore varname' -> standardized z_varname)
- CLAUDE.md: document the mlx-swift build quirks (xcodebuild for GPU
  tests, -skipPackagePluginValidation everywhere)
- 87 tests green (swift test and xcodebuild with GPU suites); app builds

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

- MetrikaKit SPM package: ZQParser, ZQPlanner, ZQEngine, ZQData, ZQStats,
  ZQGPU, ZQGraphics, ZQPlugins (Swift 6, strict concurrency)
- ZQL parser: lexer, Pratt expressions, factor variables, prefix commands,
  column-cited errors with Levenshtein verb suggestions
- ZQData: DuckDB-backed load/save (parquet, csv, json, arrow)
- ZQStats: OLS via LAPACK QR, HC0-HC3 and cluster-robust SE, summarize,
  t/F distributions accurate in the far tails
- ZQGPU: Philox4x32-10 reference RNG, counter-addressable bootstrap
- ZQEngine: session actor with use/save/gen/replace/drop/keep/summarize/
  regress/count/list/graph/bootstrap/set seed/xtset/log
- SwiftUI app (xcodegen): console with history, variables sidebar,
  Swift Charts plots; sandboxed + hardened runtime entitlements
- Tests: 44 green (parser golden, R fixtures at 1e-10, Philox KAT,
  end-to-end engine); Tests/Fixtures/generate.R; Tests/Bench harness
- scripts: check_headers.sh + pre-commit hook, make_icns.sh, release.sh

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>