Normalize internal component documentation

docs/internal/transform.md

@@ -1,47 +1,52 @@
-# Transform
+# Transform Internals
+
+Audience: developers and LLM coding agents changing `internal/transform` or transform implementations.
 
 ## Purpose
 
-`internal/transform` defines generated publication artifacts. `internal/transform/markdown` implements Markdown-to-HTML generation.
+`internal/transform` defines generated publication artifacts, transform request/response types, transform registry behavior, and transform identifiers. `internal/transform/markdown` implements Markdown-to-HTML generation.
 
-## Inputs and outputs
+## Inputs And Outputs
 
-Inputs are a validated source bundle, source backend, and transform options supplied by publish planning. Outputs include destination path, source path, transform id, generated bytes, SHA-256, and size.
-
-## Registry
-
-`internal/transform` defines the transform interface and registry. The app layer registers the Markdown implementation; publish planning receives only a resolver.
-
-## Markdown behavior
-
-Markdown sidecar mode renders files ending in `.md` to `.html` files in the same logical directory. Markdown index mode renders one selected manifest-listed Markdown file to `index.html`. Non-Markdown files do not generate sidecar outputs. Raw HTML embedded in Markdown is not passed through by the renderer.
-
-Generated HTML is deterministic for the same source content and transform configuration.
-
-See `docs/integrations/markdown.md` for the Goldmark integration contract.
-
-## Failure behavior
-
-Transform resolution fails when a requested transform id is not registered. Markdown rendering fails when the source file cannot be read or rendered. Index input selection fails when the configured input is unsafe, not listed, not Markdown, or when no configured input can be inferred from exactly one manifest-listed Markdown file. Publish planning fails when HTML output is requested and the selected transform produces no outputs for a bundle.
+Inputs are a validated source bundle, source storage backend, and transform options supplied by publish planning. Outputs are generated artifact records containing destination path, source path, transform id, generated bytes, SHA-256 digest, and byte size.
 
 ## Boundaries
 
-Transforms do not publish files, mutate source bundles, or write destination state. Publish planning selects and writes transform outputs.
+Transforms do not mutate source bundles, publish files, write destination state, choose destination actions, parse config, or inspect destinations. Publish planning decides whether generated outputs are selected and writes destination state later.
 
-The app layer owns default transform registration. The transform package does not import concrete transform implementations.
+The Goldmark renderer contract is documented in `docs/integrations/markdown.md`.
 
-## Tests
+## Config Fields Used
 
-Before changing transform behavior, inspect tests under:
+Transform packages do not read config directly. Publish planning passes effective `transform.markdown_to_html.mode` and `transform.markdown_to_html.input` values.
 
-- `internal/transform`
-- `internal/transform/markdown`
+## Adapters Used
 
-## Invariants
+Transforms read source files through `internal/storage.Backend`. The Markdown implementation uses `github.com/yuin/goldmark` for rendering.
+
+## State And Manifest Behavior
+
+Transform outputs carry metadata later projected into destination state. Markdown sidecar mode renders manifest-listed `.md` files to same-directory `.html` outputs. Markdown index mode renders one selected Markdown source to `index.html`.
+
+## Skip And Resume Behavior
+
+Transforms have no skip/resume state. They are deterministic for the same source bytes and transform options.
+
+## Failure Behavior
+
+Registry registration fails for empty names, nil transformers, and duplicate names. Transform resolution fails when publish planning requests an unregistered transform. Markdown rendering fails on source read errors, renderer errors, unsafe configured input, missing manifest input, non-Markdown input, ambiguous index input, or absent Markdown inputs.
+
+## Tests To Inspect
+
+- `internal/transform/*_test.go`
+- `internal/transform/markdown/*_test.go`
+- `internal/publish/*_test.go`
+
+## Architectural Invariants
 
 - Source bundle files are never mutated by transforms.
 - Generated outputs record destination path, source path, transform id, SHA-256, and size.
-- Markdown sidecar naming changes only the `.md` extension to `.html`.
+- Markdown sidecar naming changes only the `.md` suffix to `.html`.
 - Markdown index mode always writes `index.html`.
-- Non-Markdown source files do not generate Markdown outputs.
+- Non-Markdown source files do not generate sidecar outputs.
 - Transform registration stays outside publish planning.