Add terminal client, memory, model fallback, version and install improvements

- codecraft: full-screen terminal client (ratatui) – local tools and files,
  models via the CodeCraft server gateway or own providers (standalone with a
  guided setup), slash commands, @files, permission dialogs, resume, update
- Static Linux CLI builds (x86_64/aarch64, cargo-zigbuild) served by the
  server: /cli/install.sh and /cli/download/<target>
- Project memory (remember tool, .codecraft/memory.md) and personal memory
- Model fallback when a host is unreachable or a budget is used up
- Version/commit in UI and health, daily release check, "What's new" dialog
- PWA: install button, maskable icon, manifest id and screenshots
- Case-insensitive detection of connection errors for retries

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

cli/src/conf.rs

@@ -0,0 +1,102 @@
+//! Local configuration (~/.config/codecraft/config.toml, readable only by the user).
+
+use anyhow::{Context, Result};
+use codecraft_core::config::ProviderConfig;
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ServerLogin {
+    pub url: String,
+    pub token: String,
+    #[serde(default)]
+    pub username: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct Config {
+    /// Signed-in CodeCraft server (models, modes and rules come from there).
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub server: Option<ServerLogin>,
+    /// Model used for new sessions ("provider/model", server models as "server:provider/model").
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub default_model: Option<String>,
+    /// Permission mode for new sessions (default: auto).
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub permission_mode: Option<String>,
+    /// UI language (en, de); default from the server or $LANG.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub lang: Option<String>,
+    /// Theme override, e.g. "nord" and "dark" (default: your server theme).
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub theme: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub theme_mode: Option<String>,
+    /// Own model providers (standalone mode), same format as the server config.
+    #[serde(default, skip_serializing_if = "BTreeMap::is_empty")]
+    pub providers: BTreeMap<String, ProviderConfig>,
+}
+
+pub fn config_dir() -> PathBuf {
+    if let Some(x) = std::env::var_os("CODECRAFT_CONFIG_DIR") {
+        return PathBuf::from(x);
+    }
+    #[cfg(windows)]
+    if let Some(x) = std::env::var_os("APPDATA") {
+        return PathBuf::from(x).join("codecraft");
+    }
+    let base = std::env::var_os("XDG_CONFIG_HOME").map(PathBuf::from).unwrap_or_else(|| home().join(".config"));
+    base.join("codecraft")
+}
+
+pub fn data_dir() -> PathBuf {
+    if let Some(x) = std::env::var_os("CODECRAFT_DATA_DIR") {
+        return PathBuf::from(x);
+    }
+    #[cfg(windows)]
+    if let Some(x) = std::env::var_os("LOCALAPPDATA") {
+        return PathBuf::from(x).join("codecraft");
+    }
+    let base = std::env::var_os("XDG_DATA_HOME").map(PathBuf::from).unwrap_or_else(|| home().join(".local").join("share"));
+    base.join("codecraft")
+}
+
+pub fn home() -> PathBuf {
+    std::env::var_os("HOME").or_else(|| std::env::var_os("USERPROFILE")).map(PathBuf::from).unwrap_or_else(|| PathBuf::from("."))
+}
+
+fn path() -> PathBuf {
+    config_dir().join("config.toml")
+}
+
+impl Config {
+    pub fn load() -> Result<Self> {
+        let p = path();
+        match std::fs::read_to_string(&p) {
+            Ok(text) => toml::from_str(&text).with_context(|| format!("invalid {}", p.display())),
+            Err(_) => Ok(Self::default()),
+        }
+    }
+
+    pub fn save(&self) -> Result<()> {
+        let p = path();
+        std::fs::create_dir_all(p.parent().unwrap())?;
+        let text = format!(
+            "# CodeCraft terminal client – edit with `codecraft setup` or by hand.\n# API keys may be written as \"${{ENV_VAR}}\".\n\n{}",
+            toml::to_string_pretty(self)?
+        );
+        std::fs::write(&p, text)?;
+        #[cfg(unix)]
+        {
+            use std::os::unix::fs::PermissionsExt;
+            std::fs::set_permissions(&p, std::fs::Permissions::from_mode(0o600))?;
+        }
+        Ok(())
+    }
+
+    /// Nothing set up yet: the setup wizard runs first.
+    pub fn is_empty(&self) -> bool {
+        self.server.is_none() && self.providers.is_empty()
+    }
+}