Revise the architecture plan to reflect an input -> chunk -> process -> merge -> normalize -> output workflow

docs/roadmap/5-seriatim-input-module.md

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+# Checkpoint 5: Seriatim Input Module
+
+## Status
+
+This document describes planned work, not implemented behavior.
+
+## Goal
+
+Add the first real input source while keeping transcript-specific behavior
+isolated inside an input-stage module.
+
+This checkpoint should allow Seriatim minimal transcript JSON to become a
+generic `SourceDocument`.
+
+## Scope
+
+In scope:
+
+- `internal/modules/input/seriatim`;
+- parser for Seriatim minimal output JSON;
+- mapping into `SourceDocument` and `SourceUnit`;
+- source-document validation;
+- input adapter registry wiring;
+- fixtures and tests;
+- CLI/config path to select the input module if the CLI shell exists.
+
+Out of scope:
+
+- D&D extraction;
+- LLM extraction calls;
+- transcript-specific behavior in runner/core packages;
+- support for every possible Seriatim schema variant.
+
+## Proposed Stages
+
+### Seriatim Source Model
+
+Define module-local structs for the Seriatim minimal output schema.
+
+Expected external shape:
+
+- top-level `metadata`;
+- top-level `segments`;
+- segment `id`;
+- segment `start`;
+- segment `end`;
+- segment `speaker`;
+- segment `text`.
+
+Keep these structs in the Seriatim input module package.
+
+### Parse And Validate
+
+Implement parser and validation behavior.
+
+Validation should cover:
+
+- valid JSON;
+- required metadata fields;
+- required segment fields;
+- unique segment IDs;
+- non-empty segment text;
+- valid start/end values as appropriate.
+
+Prefer clear module-specific errors.
+
+### Map To SourceDocument
+
+Map Seriatim data into the generic source model:
+
+- segment `id` becomes `SourceUnit.ID`;
+- segment `text` becomes `SourceUnit.Text`;
+- unit kind should identify transcript-like units without requiring core
+  packages to know transcript semantics;
+- `speaker`, `start`, and `end` become unit metadata;
+- Seriatim metadata becomes document metadata.
+
+The resulting `SourceDocument` should pass core source validation.
+
+### Registry And CLI Wiring
+
+Register the module under a stable input adapter key, likely `seriatim`.
+
+If CLI support exists, add provisional selection:
+
+```sh
+notarius extract ./transcript.json --input seriatim
+```
+
+The command may still use fake extractors until checkpoint 6.
+
+### Fixtures And Tests
+
+Add fixtures and tests for:
+
+- valid Seriatim minimal transcript;
+- malformed JSON;
+- missing metadata;
+- missing or duplicate segment IDs;
+- empty segment text;
+- source-reference compatibility with generated unit IDs.
+
+## Done Criteria
+
+- `go test ./...` passes.
+- Seriatim minimal transcript JSON maps into `SourceDocument`.
+- Transcript fields do not appear in core runner contracts.
+- The input module is selectable through the registry.
+- Tests prove transcript-specific assumptions are isolated to the input module.
+
+## Review Questions
+
+- Are segment, speaker, and timestamp assumptions contained inside the input module?
+- Are unit IDs stable and suitable for source references?
+- Does the input module preserve enough metadata for transcript-oriented output later?
+- Should the input module accept only Seriatim minimal output for now?