Add model-native workspace file operations

Remove shell-escaped file mutation from the stable workspace flow by adding explicit file and patch tools across the CLI, SDK, and MCP surfaces.

This adds workspace file list/read/write plus unified text patch application, backed by new guest and manager file primitives that stay scoped to started workspaces and /workspace only. Patch application is preflighted on the host, file writes stay text-only and bounded, and the existing diff/export/reset semantics remain intact.

The milestone also updates the 3.2.0 roadmap, public contract, docs, examples, and versioning, and includes focused coverage for the new helper module and dispatch paths.

Validation:
- uv lock
- UV_CACHE_DIR=.uv-cache make check
- UV_CACHE_DIR=.uv-cache make dist-check
- real guest-backed smoke for workspace file read, patch apply, exec, export, and delete

docs/roadmap/llm-chat-ergonomics/3.2.0-model-native-workspace-file-ops.md

@@ -1,6 +1,6 @@
 # `3.2.0` Model-Native Workspace File Ops
 
-Status: Planned
+Status: Done
 
 ## Goal
 
@@ -57,3 +57,9 @@ Planned additions:
 - docs and examples that show model-native file editing instead of shell-heavy
   file writes
 - at least one real smoke scenario centered on a repro-plus-fix loop
+
+## Outcome
+
+- shipped `workspace file list|read|write` and `workspace patch apply` across CLI, SDK, and MCP
+- kept the surface scoped to started workspaces and `/workspace`
+- updated docs, help text, examples, and smoke coverage around model-native editing flows