docs(cli): add deprecation handlers and update documentation (#463)

Complete the CLI refactoring with deprecation error handlers, updated
help text, and comprehensive migration guide.

## Changes

### Deprecation Handlers
Add error handlers for all removed commands with helpful migration messages:
- `workflow put` → suggests `workflow add`
- `thread step` → suggests `thread exec`
- `thread steps` → suggests `step list`
- `thread step-details` → suggests `step show`
- `thread fork` → suggests `step fork`
- `thread kill` → suggests `thread stop` or `thread cancel`
- `thread running` → suggests `thread list --status running`

Error messages follow the format:
```
Error: Command 'X' has been removed.
Use 'Y' instead.

For more information, see: uwf help Y
```

### Help Documentation
Updated CLI help text to explain four-layer architecture:
- Main help shows architecture diagram with Chinese labels
- Command group descriptions reference layers:
  - `workflow` → "Workflow definitions (layer 1: templates)"
  - `thread` → "Thread execution (layer 2: instances)"
  - `step` → "Step results (layer 3: single cycle)"
- Deprecated commands appear in help with [DEPRECATED] tag

### README Updates
Comprehensive documentation updates:
- Added "Four-Layer Architecture" section with diagram
- Updated all command tables with new command names
- Added complete migration guide with:
  - Renamed commands table
  - Merged commands table
  - Split commands table
  - Moved commands table
  - Example deprecation error output
- Updated "Internal Structure" to show new step.ts module

## Testing
- ✅ All 124 tests pass
- ✅ Build completes successfully
- ✅ Deprecation handlers tested manually
- ✅ Help output verified for main, thread, and step commands

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/cli-workflow/src/cli.ts

@@ -52,11 +52,18 @@ const program = new Command();
 const pkg = await import("../package.json", { with: { type: "json" } });
 program
   .name("uwf")
-  .description("Stateless workflow CLI")
+  .description(
+    "Stateless workflow CLI\n\n" +
+      "Four-layer architecture:\n" +
+      "  workflow → thread → step → turn\n" +
+      "  模板定义   执行实例   单步结果   agent内部交互",
+  )
   .version(pkg.default.version, "-V, --version");
 program.option("--format <fmt>", "Output format: json or yaml", "json");
 
-const workflow = program.command("workflow").description("Workflow registry and CAS");
+const workflow = program
+  .command("workflow")
+  .description("Workflow definitions (layer 1: templates)");
 
 workflow
   .command("add")
@@ -93,7 +100,9 @@ workflow
     });
   });
 
-const thread = program.command("thread").description("Thread lifecycle and execution");
+const thread = program
+  .command("thread")
+  .description("Thread execution (layer 2: instances)");
 
 thread
   .command("start")
@@ -240,7 +249,7 @@ thread
     },
   );
 
-const step = program.command("step").description("Step operations");
+const step = program.command("step").description("Step results (layer 3: single cycle)");
 
 step
   .command("list")
@@ -292,6 +301,103 @@ step
     });
   });
 
+// ── Deprecation Handlers ──────────────────────────────────────────────────────
+// These commands have been removed. Show helpful error messages.
+
+workflow
+  .command("put")
+  .description("[DEPRECATED] Use 'workflow add' instead")
+  .argument("<file>", "Workflow YAML file")
+  .action(() => {
+    process.stderr.write(`Error: Command 'workflow put' has been removed.
+Use 'workflow add' instead.
+
+For more information, see: uwf help workflow add
+`);
+    process.exit(1);
+  });
+
+thread
+  .command("step")
+  .description("[DEPRECATED] Use 'thread exec' instead")
+  .argument("<thread-id>", "Thread ULID")
+  .allowUnknownOption()
+  .action(() => {
+    process.stderr.write(`Error: Command 'thread step' has been removed.
+Use 'thread exec' instead.
+
+For more information, see: uwf help thread exec
+`);
+    process.exit(1);
+  });
+
+thread
+  .command("steps")
+  .description("[DEPRECATED] Use 'step list' instead")
+  .argument("<thread-id>", "Thread ULID")
+  .action(() => {
+    process.stderr.write(`Error: Command 'thread steps' has been removed.
+Use 'step list' instead.
+
+For more information, see: uwf help step list
+`);
+    process.exit(1);
+  });
+
+thread
+  .command("step-details")
+  .description("[DEPRECATED] Use 'step show' instead")
+  .argument("<step-hash>", "Step hash")
+  .action(() => {
+    process.stderr.write(`Error: Command 'thread step-details' has been removed.
+Use 'step show' instead.
+
+For more information, see: uwf help step show
+`);
+    process.exit(1);
+  });
+
+thread
+  .command("fork")
+  .description("[DEPRECATED] Use 'step fork' instead")
+  .argument("<step-hash>", "Step hash")
+  .action(() => {
+    process.stderr.write(`Error: Command 'thread fork' has been removed.
+Use 'step fork' instead.
+
+For more information, see: uwf help step fork
+`);
+    process.exit(1);
+  });
+
+thread
+  .command("kill")
+  .description("[DEPRECATED] Use 'thread stop' or 'thread cancel' instead")
+  .argument("<thread-id>", "Thread ULID")
+  .action(() => {
+    process.stderr.write(`Error: Command 'thread kill' has been removed.
+Use 'thread stop' to stop background execution (keep thread active),
+or 'thread cancel' to cancel and archive the thread.
+
+For more information, see:
+  uwf help thread stop
+  uwf help thread cancel
+`);
+    process.exit(1);
+  });
+
+thread
+  .command("running")
+  .description("[DEPRECATED] Use 'thread list --status running' instead")
+  .action(() => {
+    process.stderr.write(`Error: Command 'thread running' has been removed.
+Use 'thread list --status running' instead.
+
+For more information, see: uwf help thread list
+`);
+    process.exit(1);
+  });
+
 const skill = program.command("skill").description("Built-in skill references for agents");
 
 skill