feat: add deterministic preview rendering

SLICE_HISTORY.md

@@ -128,3 +128,51 @@ DFG-3: add isolated, hash-bound proposal changesets without canonical write auth
 ### Next gate
 
 DFG-4: add deterministic previews and confined renderer orchestration without canonical application.
+
+## DFG-4 deterministic previews and renderer orchestration
+
+### Changed
+
+- Added optional project-declared template, preview, view, and derived-output configuration with
+  strict root confinement, overlap rejection, stable view IDs, and configured size limits.
+- Added an explicit renderer protocol backed by a closed built-in registry. Configuration cannot
+  name commands, modules, executable paths, or undeclared renderers.
+- Added the `generic_html` renderer with pinned `markdown-it-py` CommonMark parsing, disabled raw
+  HTML, fixed safe template tokens, deterministic node ordering, navigation, metadata, content, and
+  relationship output.
+- Added render identities covering canonical and proposal inputs, node and edge identities, view
+  configuration, template hash, renderer contract, and exact Markdown parser version.
+- Added atomic per-view CLI rendering, non-writing render status, and isolated changeset previews.
+  Input changes detected before replacement preserve prior output.
+- Added `docforge_preview_changeset` to MCP and made `docforge_render_status` report configured view
+  hashes and state. MCP cannot render declared project output or select a renderer or command.
+- Split shared configuration validation, render configuration, renderer contract, and orchestration
+  into focused modules instead of expanding the project loader or MCP translation layer.
+
+### Verification
+
+- Renderer tests prove repeatable identities and bytes, current and stale status, isolated previews,
+  escaped raw HTML, CommonMark conversion, unchanged canonical and declared output, configured
+  limits, symbolic-link rejection, and preservation of prior output after invalid or changing input.
+- Configuration tests reject command-like fields, unsupported renderer IDs, protected output paths,
+  undeclared views, oversized templates and output, and unsafe symbolic links.
+- CLI tests cover declared render, render status, isolated preview, and structured unknown-view
+  failure. Protocol tests exercise preview through the official in-memory MCP transport and prove
+  declared output remains absent.
+- Ruff formatting and lint checks, Python compilation, all five JSON schema parses, and the locked
+  dependency check passed.
+- All 35 core, CLI, changeset, concurrency, renderer, in-memory MCP, and real stdio tests passed with
+  `ResourceWarning` treated as an error.
+
+### Limits
+
+- The first built-in renderer emits one self-contained HTML file per view. Multi-file asset bundles
+  and project-specific view models remain future adapter work.
+- Preview generation validates proposals but does not apply them to canonical documentation.
+- Declared project-output rendering is an explicit local CLI integration action, not an MCP tool.
+- Worldforge and unrelated-project adapters remain unopened.
+
+### Next gate
+
+DFG-5: reproduce Worldforge semantics and generated output through a shadow-only adapter without
+changing the live workflow.