Restructure package: pure-Julia core, D-VARS extensions, opt-in Python validation

- Remove PyCall/Conda/Plots/Optim/Printf/Integrals from package deps; the
  package no longer installs a Python stack on 'pkg> add'
- Delete deps/build.jl; pip setup moves to test/python_validation/setup.jl
- Move varstool comparison tests to test/python_validation/ with their own
  environment (see its README for how to run them)
- Provide D-VARS as package extensions: dvars_sensitivities activates with
  DataFrames+Surrogates, dvars_sensitivities_robust with DataFrames+BlackBoxOptim;
  debug output now behind verbose=false; 1-D quadrature via QuadGK
- Move pce_sensitivities into examples/sobol_g_dvars.jl (its only caller)
- Fix UndefVarError in generate_vars_samples for N == 0
- Stop mutating the global RNG in sampling, G-VARS and bootstrap (local RNGs)
- Index info once in vars_analyse/gvars_analyse instead of findall per
  star/dim: ~150x faster on d=20, N=256, bit-identical results
- Add pure-Julia test suite (sampling structure, analytical Ishigami/Sobol-G
  accuracy, G-VARS, bootstrap, both D-VARS extensions)
- Add CI/TagBot/CompatHelper workflows and Documenter docs
- Untrack Manifest.toml, add .gitignore, examples/Project.toml
- Widen compat to Julia 1.10 LTS; bump version to 0.3.0
- README: fix broken code fence; update Dependencies section for the new
  optional Python validation and D-VARS extensions

Author: Msturroc

.github/workflows/CI.yml

@@ -0,0 +1,63 @@
+name: CI
+on:
+  push:
+    branches:
+      - main
+    tags: ['*']
+  pull_request:
+  workflow_dispatch:
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
+jobs:
+  test:
+    name: Julia ${{ matrix.version }} - ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 60
+    strategy:
+      fail-fast: false
+      matrix:
+        version:
+          - '1.10'
+          - '1'
+        os:
+          - ubuntu-latest
+        include:
+          - version: '1'
+            os: windows-latest
+          - version: '1'
+            os: macOS-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: julia-actions/setup-julia@v2
+        with:
+          version: ${{ matrix.version }}
+      - uses: julia-actions/cache@v2
+      - uses: julia-actions/julia-buildpkg@v1
+      - uses: julia-actions/julia-runtest@v1
+      - uses: julia-actions/julia-processcoverage@v1
+      - uses: codecov/codecov-action@v4
+        with:
+          files: lcov.info
+  docs:
+    name: Documentation
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      statuses: write
+    steps:
+      - uses: actions/checkout@v4
+      - uses: julia-actions/setup-julia@v2
+        with:
+          version: '1'
+      - uses: julia-actions/cache@v2
+      - name: Build and deploy docs
+        run: |
+          julia --project=docs -e '
+            using Pkg
+            Pkg.develop(PackageSpec(path=pwd()))
+            Pkg.instantiate()'
+          julia --project=docs docs/make.jl
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          DOCUMENTER_KEY: ${{ secrets.DOCUMENTER_KEY }}

.github/workflows/CompatHelper.yml

@@ -0,0 +1,29 @@
+name: CompatHelper
+on:
+  schedule:
+    - cron: 0 0 * * *
+  workflow_dispatch:
+permissions:
+  contents: write
+  pull-requests: write
+jobs:
+  CompatHelper:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check if Julia is already available in the PATH
+        id: julia_in_path
+        run: which julia
+        continue-on-error: true
+      - name: Install Julia, but only if it is not already available in the PATH
+        uses: julia-actions/setup-julia@v2
+        with:
+          version: '1'
+        if: steps.julia_in_path.outcome != 'success'
+      - name: Use Julia cache
+        uses: julia-actions/cache@v2
+      - name: Pkg.add("CompatHelper")
+        run: julia -e 'import Pkg; Pkg.add("CompatHelper")'
+      - name: CompatHelper.main()
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: julia -e 'import CompatHelper; CompatHelper.main()'

.github/workflows/TagBot.yml

@@ -0,0 +1,31 @@
+name: TagBot
+on:
+  issue_comment:
+    types:
+      - created
+  workflow_dispatch:
+    inputs:
+      lookback:
+        default: '3'
+permissions:
+  actions: read
+  checks: read
+  contents: write
+  deployments: read
+  issues: read
+  discussions: read
+  packages: read
+  pages: read
+  pull-requests: read
+  repository-projects: read
+  security-events: read
+  statuses: read
+jobs:
+  TagBot:
+    if: github.event_name == 'workflow_dispatch' || github.actor == 'JuliaTagBot'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: JuliaRegistries/TagBot@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          ssh: ${{ secrets.DOCUMENTER_KEY }}

.gitignore

@@ -0,0 +1,5 @@
+Manifest.toml
+docs/build/
+*.jl.cov
+*.jl.*.cov
+*.jl.mem