Rewrite internal documentation for current stage and state contracts

docs/internal/stage-trim.md

@@ -1,75 +1,28 @@
 # Stage: trim
 
 ## Purpose
-Optionally trim the final transcript to session bounds; always produce a durable final-trimmed transcript.
+Produce a final-trimmed transcript; optionally generate bounds-driven trim.
 
-## Inputs and Outputs
-Inputs:
+## Inputs
 - `transcripts/final.json`
 
-Outputs:
+## Outputs
 - `transcripts/final.trimmed.json` (or configured trim output path)
 - when trim enabled: `artifacts/session_bounds.json`
 
-## Boundaries
-Owns:
-- Trim-enabled switch behavior
-- Bounds generation via Scriptorium artifact run
-- Bounds validation against final transcript
-- Keep-selector derivation and Seriatim trim invocation
-- Copy-through behavior when disabled or bounds indicate unchanged transcript
+## Key Behavior
+When `trim.enabled=false`:
+- copies normalized transcript to trimmed output.
 
-Does not own:
-- Upstream normalization
-- Downstream artifact analysis
+When `trim.enabled=true`:
+- runs Scriptorium bounds artifact generation;
+- optionally runs render-debug output generation;
+- validates bounds payload against transcript;
+- derives keep selector;
+- either copies unchanged transcript or runs Seriatim trim;
+- validates trimmed transcript and materializes bounds output.
 
-## Config Fields Used
-- `session.session_id`
-- `session.campaign`
-- `pipeline.workspace.root`
-- `pipeline.trim.enabled`
-- `pipeline.trim.output_path`
-- `pipeline.trim.bounds.prompt_id`
-- `pipeline.trim.bounds.profile_id`
-- `pipeline.trim.bounds.timeout`
-- `pipeline.trim.bounds.output_path`
-- `pipeline.trim.bounds.transcript_input_name`
-- `pipeline.trim.bounds.render_debug`
-- `pipeline.trim.bounds.render_output_path`
-- `pipeline.seriatim.binary`
-- `pipeline.seriatim.timeout`
-- `pipeline.scriptorium.binary`
-- `pipeline.scriptorium.config_path`
-- `pipeline.scriptorium.timeout`
-
-## External Adapters Used
-- Scriptorium adapter:
-  - optional `RenderArtifact` for bounds debug render
-  - `RunArtifact` for bounds output
-- Seriatim adapter:
-  - `Trim` when bounds indicate trimming is required
-
-## State and Manifest Behavior
-- Reads final transcript from normalize manifest outputs when available; falls back to canonical path.
-- Uses run-local outputs/logs/reports/config/scratch paths when run layout is enabled.
-- Materializes canonical final-trimmed transcript and session bounds when trim is enabled.
-- Records bounds diagnostics, trim action, keep selector, and adapter metadata.
-
-## Skip and Resume Behavior
-- Runner-level skip applies when already succeeded and not forced.
-- Forced reruns can stale downstream succeeded stages.
-- When `trim.enabled=false`, stage still succeeds by copying final to final-trimmed output.
-
-## Failure Behavior
-- Fails on missing/invalid final transcript.
-- With trim enabled, fails on missing adapters/config, bounds generation/validation errors, invalid bounds JSON, invalid range/segment ids, trim adapter failures, or invalid final-trimmed output.
-
-## Tests to Inspect Before Changing
-- `internal/stage/trim_test.go`
-- `internal/adapters/scriptorium/subprocess_test.go`
-- `internal/adapters/seriatim/subprocess_test.go`
-
-## Architectural Invariants
-- Trim never falls back to polished transcript; final transcript is required input.
-- `session_bounds` output exists only for enabled trim path.
-- Render-debug artifacts are diagnostics and not declared stage outputs.
+## Invariants
+- normalized transcript is required input.
+- bounds output exists only in enabled trim path.
+- render-debug output is diagnostic and not a declared stage output.