feat(src): add if-viz CLI tool for local manifest visualisation

.gitignore

@@ -14,3 +14,4 @@ src/__tests__/integration/manifest
 examples/outputs
 with-plugins/*
 !with-plugins/Dockerfile
+.scratch/

CLAUDE.md

@@ -0,0 +1,96 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+**Impact Framework (IF)** is a TypeScript framework by the Green Software Foundation for modelling, measuring, and monitoring the environmental impacts of software. It uses a plugin-based pipeline architecture that processes YAML manifest files describing component trees and computation pipelines.
+
+## Common Commands
+
+```bash
+# Build
+npm run build          # TypeScript compilation to /build
+
+# Test
+npm test                                          # Run all tests (Jest, verbose)
+npm test -- src/__tests__/if-run/lib/compute.test.ts  # Run a single test file
+npm run coverage                                  # Generate coverage report
+
+# Lint
+npm run lint           # GTS (Google TypeScript Style) linting
+npm run fix            # Auto-fix lint issues
+
+# CLI tools (after build)
+npx if-run -m <manifest.yaml>           # Run a manifest
+npx if-run -m <manifest.yaml> --debug   # Run with debug logging
+npx if-check -m <manifest.yaml>         # Validate a manifest
+npx if-diff -s <source.yaml> -t <target.yaml>  # Compare outputs
+npx if-csv -m <manifest.yaml>           # Export to CSV
+npx if-api                              # Start REST API server (port 3000)
+```
+
+## Architecture
+
+### Execution Flow (if-run)
+
+1. Parse CLI args → load manifest YAML → inject environment variables → validate with Zod
+2. **Initialize**: Load plugins from manifest's `initialize.plugins` and register in plugin storage
+3. **Compute**: Depth-first traversal of the component tree — for each leaf node: merge defaults → observe → regroup → compute
+4. **Aggregate**: Apply horizontal (time) and/or vertical (component) aggregation
+5. **Exhaust**: Write results to YAML/console
+
+Pipeline phases (observe, regroup, compute) can be run in isolation via `--observe`, `--regroup`, `--compute` flags.
+
+### Source Layout
+
+- `src/if-run/` — Main execution engine: pipeline orchestration, plugin loading, aggregation, output
+- `src/if-run/builtins/` — ~19 built-in plugins (multiply, sum, divide, sci, csv-lookup, time-sync, etc.)
+- `src/if-api/` — Express v5 REST API server with the same core execution as if-run
+- `src/if-check/`, `src/if-csv/`, `src/if-diff/`, `src/if-env/`, `src/if-merge/`, `src/if-metadata-check/` — Auxiliary CLI tools
+- `src/common/` — Shared utilities (logger, Zod validation, YAML I/O, filesystem helpers)
+- `src/__tests__/` — Test suites mirroring source structure
+- `src/__mocks__/` — Jest mocks
+
+### Plugin System
+
+Plugins implement the `PluginInterface` from `@grnsft/if-core/types` and are created via `PluginFactory` from `@grnsft/if-core/interfaces`:
+
+```typescript
+export const MyPlugin = PluginFactory({
+  configValidation: (config: ConfigParams) => { /* Zod validation */ },
+  inputValidation: (input: PluginParams, config: ConfigParams) => { /* Zod validation */ },
+  implementation: async (inputs: PluginParams[], config: ConfigParams) => { /* return transformed inputs */ },
+  allowArithmeticExpressions: [],
+});
+```
+
+Built-in plugins use `path: 'builtin'` in the manifest. External plugins use npm module paths or GitHub URLs. The plugin storage (`src/if-run/util/plugin-storage.ts`) is a simple name→instance registry.
+
+### Manifest Structure
+
+Manifests are YAML files with: `name`, `initialize.plugins` (plugin definitions with path, method, config, mapping), `tree` (component hierarchy with pipeline, defaults, inputs), and optional `aggregation` settings. Validated at runtime using Zod schemas in `src/common/util/validations.ts`.
+
+### Key Dependencies
+
+- `@grnsft/if-core` — Core types, interfaces (`PluginFactory`), error classes, aggregation constants
+- `zod` — Schema validation throughout
+- `js-yaml` — YAML parsing/generation
+- `luxon` — Date/time handling (used in time-sync, time-converter plugins)
+
+## Commit Conventions
+
+Conventional commits enforced via commitlint. Scope is **required**.
+
+- **Types**: feat, fix, docs, chore, style, refactor, ci, test, revert
+- **Scopes**: util, lib, types, src, package, config, mocks, .github, .husky, scripts, builtins, plugins, integration, doc, manifests, release, .commitlint
+
+Example: `feat(builtins): add new interpolation method`
+
+## Testing
+
+Tests are in `src/__tests__/` mirroring the source tree. Jest with ts-jest. Mocks live in `src/__mocks__/`. Coverage excludes config and types directories.
+
+## API Server Notes
+
+The API server (`if-api`) disables Shell, CSVImport, and CSVLookup plugins by default for security. Uses request-scoped context storage to prevent cross-request contamination.