rename: fork mcphost to kit (github.com/mark3labs/kit)

Rename the entire project from mcphost to kit, including:
- Go module path and all import paths
- SDK type MCPHost -> Kit, file renames mcphost.go -> kit.go
- CLI command name, usage strings, UI labels (KIT in literature)
- Config paths (.mcphost -> .kit), env prefix (MCPHOST_ -> KIT_)
- Data/credential/hooks directory paths
- Remove legacy .mcp config fallbacks
- Session metadata field (mcphost_version -> kit_version)
- MCP client identity name
- Build output, goreleaser binary name
- All documentation, examples, scripts, and test files

contribute/contribute.md

@@ -3,12 +3,12 @@ Thanks for your contribution, you can follow these step to run this repo and deb
 ## Run demo
 1. clone this repo to your work dir.
     ```bash
-    git clone https://github.com/mark3labs/mcphost.git
+    git clone https://github.com/mark3labs/kit.git
     ```
 
 2. enter the `contribute` dir.
     ```bash
-    cd mcphost/contribute
+    cd kit/contribute
     ```
 
 3. run `build.sh` to build your binary file.
@@ -22,7 +22,7 @@ Thanks for your contribution, you can follow these step to run this repo and deb
       vi boost.sh
    ```
 
-5. run `boost.sh` to run your mcphost, if you don't want run it in debug model, you can delete the `--debug` flag in `boost.sh`.
+5. run `boost.sh` to run kit, if you don't want run it in debug model, you can delete the `--debug` flag in `boost.sh`.
    ```bash
       ./boost.sh
    ```