V1]individual] auto label suggestion

[clintjeff2]

Motivation

• Provide an isolated, deterministic V1 core engine for the Auto Label Suggestion tool so the feature can be reviewed and iterated on without touching the main app.
• Offer a small, folder-local API and types that capture inputs, outputs, loading/error states, and privacy constraints for future UI integration.

Description

• Added a folder-local deterministic label engine in tools/v1/individual/auto-label-suggestion/ including services.ts, types.ts, and an index.ts export surface that exposes suggestAutoLabels and validateAutoLabelEmail.
• Implemented a documented label taxonomy (AUTO_LABEL_TAXONOMY) and rule-based matching using local regex patterns, evidence extraction, scoring, priority-based ranking, and a MAX_SUGGESTIONS cap of three.
• Returned explainable suggestions with label, confidence (high|medium|low), reason, and evidence, and preserved existing user labels separately from suggestions.
• Added folder-local Vitest tests (services.test.ts) and a vitest config plus README and review notes that document the API, inputs/outputs, and privacy/no-network guarantees.

Testing

• Added fixture-backed unit tests that validate the taxonomy, fixture expectations, ranking, explainability, existing-label preservation, and deterministic validation paths using fixtures/email-label-cases.json and services.test.ts (tests are present but not executed to completion in this environment).
• Attempted to run npm exec vitest run -- --config tools/v1/individual/auto-label-suggestion/vitest.config.ts, but the run failed due to registry access returning 403 Forbidden when fetching vitest (dependencies are not installed here).
• Attempted to run npx tsc --noEmit --pretty false, but type checking failed in this environment because local dependency type definitions (e.g., vite/client) are not installed.

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Closes #325