Migrate internal architecture docs to docs/internal

docs/internal/pipeline.md

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+# Audita Internal Pipeline
+
+## Scope
+
+This document describes the implemented `audita process` pipeline.
+
+## Inputs
+
+Pipeline inputs are:
+- effective config (`internal/core/config`);
+- transcript JSON (`internal/core/schema`);
+- glossary YAML (`internal/core/schema`).
+
+## Pipeline Phases
+
+1. Input loading and schema validation
+- transcript and glossary files are read and parsed.
+- schema failures stop the run with `transcript_schema` or `glossary_schema`.
+
+2. Normalization
+- canonical transcript segments are normalized by configured gap/duration/token settings.
+- normalization summary artifacts are written.
+
+3. Chunking
+- normalized transcript is chunked with configured max/min tokens and target sections.
+
+4. Module proposal generation
+- runner executes configured module instances in sequence.
+- each module proposes corrections per section.
+- per-section proposal generation can run concurrently.
+
+5. Validator filtering
+- validators run on candidate proposals before apply.
+- deterministic validators run before LLM-backed validators.
+- LLM validator inputs are batched by max prompt token limit.
+
+6. Deterministic apply
+- approved proposals are applied via replacement policy.
+- applied/skipped/rejected outcomes are recorded.
+
+7. Output and reporting
+- final transcript is serialized with selected output schema.
+- report, utilization diagnostics, and correction ledger are written.
+- retention policy is applied to run directory.
+
+## Runner Outputs
+
+`runner.Run` returns:
+- final transcript;
+- per-module results;
+- utilization diagnostics.
+
+CLI/reporting then map this into process report and diagnostics artifacts.
+
+## Failure Behavior
+
+Representative failure phases include:
+- `run_dir_creation`
+- `transcript_read`, `glossary_read`
+- `transcript_schema`, `glossary_schema`
+- `chunking`
+- `runner_setup`, `runner_execution`
+- `output_schema`, `serialization`, `output_write`, `stdout_write`
+
+When diagnostics are available, failure stderr includes diagnostics path.
+
+## Invariants
+
+- module execution order follows configured module sequence;
+- proposal/validator nondeterminism is isolated before deterministic apply;
+- proposal indices are assigned deterministically by section order;
+- output/report artifacts are generated from run results, not speculative state.
+
+## Key Tests
+
+- `internal/framework/runner/runner_test.go`
+- `internal/framework/proposal_generation/*_test.go`
+- `internal/cli/run_test.go`
+- `cmd/audita/main_integration_test.go`