Chat tabs, chat mode, own modes, compaction notice, CLI binaries again

- Terminals and file managers as tabs of a chat; chat terminals keep running on
  the server (no idle timeout) and re-attach from any device
- "Just chat" in New session and a built-in chat mode with a lean prompt and only
  web tools; custom modes with kind (coding/conversation), read-only and tool picker
- Mode selector as a dropdown
- The chat shows running compactions (automatic: tokens and share of the limit)
  and labels summaries
- Docker image builds and serves the terminal client binaries again
- Fix: atomic session updates; background title/usage writes no longer undo each
  other (auto compaction triggered one turn late)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -173,15 +173,14 @@ Anthropic, OpenAI, Gemini, OpenRouter, opencode or a local model server (Ollama,
 llama.cpp, vLLM – detected automatically); both can be mixed.
 
 ```sh
-cargo install --locked --git https://git.familie-zink.org/zink/codecraft codecraft-cli
+curl -fsSL https://<your-codecraft-server>/cli/install.sh | sh   # Linux x86_64 / aarch64
 codecraft login            # server URL, user name, password → creates an API token
 codecraft                  # start in the current folder; /help lists the commands
 ```
 
-There are no prebuilt binaries yet, so the client is installed from source (needs a Rust
-toolchain). A server that has binaries in `CODECRAFT_CLI_DIR` (`codecraft-linux-x86_64`,
-`codecraft-linux-aarch64`) also offers `curl -fsSL https://<your-server>/cli/install.sh | sh`
-and `codecraft update`.
+The Docker image ships static binaries for Linux x86_64 and aarch64; the server offers them
+for download (*Settings → Account*) and `codecraft update` fetches new versions from it. Other
+platforms: `cargo install --locked --git https://git.familie-zink.org/zink/codecraft codecraft-cli`.
 
 ## Automations
 
@@ -335,7 +334,7 @@ web/     React + Vite PWA
   src/i18n        English (reference) and German
 ```
 
-The Docker build cross-compiles the server with
+The Docker build cross-compiles the server and the terminal client with
 [cargo-zigbuild](https://github.com/rust-cross/cargo-zigbuild), so a multi-arch image builds
 quickly on either architecture:
 `docker buildx build --platform linux/amd64,linux/arm64 -t <registry>/codecraft:<version> --push .`
@@ -353,7 +352,7 @@ Translations: copy `web/src/i18n/en.ts`, translate the values and register the l
 
 Early, but in daily use. See the [changelog](CHANGELOG.md). Planned next:
 
-- Prebuilt terminal client binaries (Linux, macOS, Windows)
+- Terminal client builds for macOS and Windows
 - MCP OAuth, resources and prompts
 - The OpenAI Responses API