Add roadmap documents for the initial architecture

docs/roadmap/2-framework-composition.md

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+# Checkpoint 2: Framework Composition
+
+## Status
+
+This document describes planned work, not implemented behavior.
+
+## Goal
+
+Prove the core contracts compose before adding real adapters, real extractors,
+or portable Audita infrastructure.
+
+This checkpoint should produce a minimal runner that can execute fake registered
+components from source input to artifact output in tests.
+
+## Scope
+
+In scope:
+
+- input adapter registry;
+- extractor registry;
+- validator decision model;
+- decision-cardinality checks;
+- minimal runner;
+- fake-component runner tests.
+
+Out of scope:
+
+- real input parsing;
+- real LLM calls;
+- prompt assets;
+- response schema assets;
+- diagnostics run directory;
+- real D&D artifact schemas.
+
+## Proposed Stages
+
+### Stage 1: Input Adapter Registry
+
+Add a registry for `InputAdapter` constructors or instances.
+
+The registry should:
+
+- reject empty keys;
+- reject duplicate registrations;
+- return clear errors for unknown keys;
+- avoid importing concrete adapter packages from core contracts.
+
+### Stage 2: Extractor Registry
+
+Add a registry for extractor constructors or instances.
+
+The registry should:
+
+- support stable extractor keys;
+- support repeated extractor instances if needed later;
+- return clear errors for unknown keys;
+- avoid domain-specific logic.
+
+### Stage 3: Validator Decisions
+
+Add validator decision types and cardinality checks.
+
+Each validator should return exactly one decision for each candidate artifact it
+receives.
+
+Decision fields should include:
+
+- candidate index;
+- approved flag;
+- reason code;
+- message;
+- optional diagnostics path.
+
+### Stage 4: Minimal Runner
+
+Add a runner that can:
+
+1. receive a `SourceDocument`;
+2. execute configured extractors;
+3. validate candidate artifacts;
+4. return approved and rejected artifacts.
+
+Keep source chunking optional or stubbed at this checkpoint. The runner may
+operate on whole documents only until source-unit chunking is added later.
+
+### Stage 5: Runner Tests With Fakes
+
+Add tests with fake components that prove:
+
+- registered fake extractors run in configured order;
+- validators filter candidates deterministically;
+- decision cardinality failures are surfaced;
+- approved and rejected artifacts are returned in stable order.
+
+## Done Criteria
+
+- `go test ./...` passes.
+- Fake adapter/extractor/validator registrations work in tests.
+- The runner operates on `SourceDocument`, not transcript-specific structures.
+- The runner does not import concrete D&D extractor packages.
+
+## Review Questions
+
+- Does the runner know only about sources, extractors, validators, and artifacts?
+- Are registries simple enough to evolve?
+- Are validation decisions expressive enough for deterministic and LLM-backed
+  validators?
+- Is any domain-specific behavior creeping into framework packages?