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/session.rs

@@ -0,0 +1,90 @@
+//! Local sessions (~/.local/share/codecraft/sessions/<id>.json).
+
+use anyhow::Result;
+use codecraft_core::types::{Message, Part, Usage, new_id, now_ms};
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+use std::path::PathBuf;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct LocalSession {
+    pub id: String,
+    pub title: String,
+    pub cwd: String,
+    pub model: String,
+    pub mode: String,
+    pub permission_mode: String,
+    pub created_at: i64,
+    pub updated_at: i64,
+    pub messages: Vec<Message>,
+    #[serde(default)]
+    pub usage: Usage,
+    #[serde(default)]
+    pub cost: f64,
+    #[serde(default)]
+    pub todos: Value,
+    /// Tokens of the last request (context fill).
+    #[serde(default)]
+    pub context_tokens: u64,
+}
+
+fn dir() -> PathBuf {
+    crate::conf::data_dir().join("sessions")
+}
+
+impl LocalSession {
+    pub fn new(cwd: &str, model: &str, mode: &str, permission_mode: &str) -> Self {
+        let now = now_ms();
+        Self {
+            id: new_id(),
+            title: String::new(),
+            cwd: cwd.into(),
+            model: model.into(),
+            mode: mode.into(),
+            permission_mode: permission_mode.into(),
+            created_at: now,
+            updated_at: now,
+            messages: vec![],
+            usage: Usage::default(),
+            cost: 0.0,
+            todos: Value::Null,
+            context_tokens: 0,
+        }
+    }
+
+    pub fn save(&mut self) -> Result<()> {
+        if self.messages.is_empty() {
+            return Ok(());
+        }
+        self.updated_at = now_ms();
+        std::fs::create_dir_all(dir())?;
+        let tmp = dir().join(format!("{}.json.tmp", self.id));
+        std::fs::write(&tmp, serde_json::to_vec(self)?)?;
+        std::fs::rename(tmp, dir().join(format!("{}.json", self.id)))?;
+        Ok(())
+    }
+
+    pub fn load(id: &str) -> Result<Self> {
+        Ok(serde_json::from_slice(&std::fs::read(dir().join(format!("{id}.json")))?)?)
+    }
+
+    /// Messages the model sees: everything from the last summary on.
+    pub fn active(&self) -> Vec<Message> {
+        let start = self.messages.iter().rposition(|m| m.parts.iter().any(|p| matches!(p, Part::Summary { .. }))).unwrap_or(0);
+        self.messages[start..].to_vec()
+    }
+}
+
+/// Sessions (newest first), optionally only those of one folder.
+pub fn list(cwd: Option<&str>) -> Vec<LocalSession> {
+    let mut out: Vec<LocalSession> = std::fs::read_dir(dir())
+        .into_iter()
+        .flatten()
+        .flatten()
+        .filter(|e| e.path().extension().is_some_and(|x| x == "json"))
+        .filter_map(|e| serde_json::from_slice::<LocalSession>(&std::fs::read(e.path()).ok()?).ok())
+        .filter(|s| cwd.is_none_or(|c| s.cwd == c))
+        .collect();
+    out.sort_by_key(|s| std::cmp::Reverse(s.updated_at));
+    out
+}