chore(plugin): sync marketplace.json to 0.2.1 + document updating

The Claude Code marketplace manifest at .claude-plugin/marketplace.json
was still pointing at 0.1.1 — both metadata.version and plugins[].version.
Bumping to 0.2.1 so /plugin marketplace update task-journal surfaces the
update for end users.

README gains an Updating section with the exact slash commands and the
cargo install --force step (binaries live on crates.io, plugin doesnt
bundle them).

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

Author: Shahinyanm

.claude-plugin/marketplace.json

@@ -6,14 +6,14 @@
   },
   "metadata": {
     "description": "Task Journal — append-only reasoning chain memory for AI-coding tasks",
-    "version": "0.1.1"
+    "version": "0.2.1"
   },
   "plugins": [
     {
       "name": "task-journal",
       "source": "./plugin",
       "description": "Append-only journal of AI-coding task reasoning chains. Captures hypotheses, decisions, rejections, evidence — renders compact resume packs so an agent can pick up a 2-week-old task with full context.",
-      "version": "0.1.1",
+      "version": "0.2.1",
       "author": {
         "name": "Digital-Threads"
       },

README.md

@@ -37,6 +37,30 @@ cd Task-Journal
 cargo install --path crates/tj-cli --path crates/tj-mcp
 ```
 
+## Updating
+
+If you installed via the Claude Code marketplace, run these inside Claude Code:
+
+```
+/plugin marketplace update task-journal
+/plugin update task-journal@task-journal
+```
+
+Then refresh the Rust binaries (the plugin doesn't bundle them — they live on crates.io):
+
+```bash
+cargo install task-journal-cli task-journal-mcp --force
+```
+
+Restart Claude Code so the new MCP server is picked up, and verify:
+
+```bash
+task-journal --version       # 0.2.1
+task-journal-mcp --version   # 0.2.1
+```
+
+If you installed from source, `git pull && cargo install --path crates/tj-cli --path crates/tj-mcp --force` does the same thing.
+
 ## Quick Start
 
 ```bash